Swtpc Ac-30 User manual

Assembly

Instructions

AC-30

Audio

Cassette

Interface

©

Introduction

Cassette

tape

is

one

of

the

most

flexible

and

least

expensive

means

of

mass

data

storage

for

computer

systems.

When

compared

to

paper

tape

readers

and

punches,

you'll

find that

although

the

paper

tape

readers

can

be

made

rather

inexpensively,

the

punches

cannot.

Paper

tape

systems

are

typically

slower

and

the

punched

tapes

cannot

of

course

be

repunched

and

used

over

and

over

again,

as

you

can

with

cassettes.

Disk

systems

on

the

other

hand

offer

significant

advantages

over

cassettes

but

‘are

still

too

expensive

for

many

applications,

and

for

most

hobbyists.

Even

those

lucky

enough

to

have

a

disk

system

still

need

a

more

universal

‘medium

for

exchanging

programs.

—

Although

there

are

several

commercial

digital

cassette

tape

decks

on

the

market

today,

recording

techniques

vary

and

they

are

of

course

much

more

ex-

pensive

than

the

average

audio

cassette

unit.

As

could

be

expected

most

hob-

byist

computer

system

mass

data

storage,

designs

have

been

based

on

the

audio

cassette

recorder.

ee

The

use

of

inconsistent:

recording

techniques

among

‘the

various

manufact-

urers

makes

it

impossible

for

example

to

record

a

program,

or

data

tape

on

a

SWIPC

6800

Computer

System

and

play

it

back

on

a

MITS

680

Computer

System.

In

order

to

coordinate

manufacturer

design

efforts,

and

exploit

the

most

ef-

fective

recording

technique,

BYTE

Magazine

of

Peterborough,

New

Hampshire,

03458

held

a

symposium

in

the

Fall

of

1975

in

Kansas

City

in

an

attempt

to

establish

a

recording

standard

for

the

storage

of

digital

data

on

audio

cas-

sette

recorders.

The

standard

which

was

adopted

has

been

tested

and

fully

sup-

ported

by

Southwest

Technical

Products

Corporation.

It

appears

to

be

the

best

compromise

between

economy

and

reliability.

Although

complete

details

are

contained

in

the

Feb.,

1976

issue

of

BYTE

Magazine,

the

recording

philosophy

is

to

record

data

serially

using

the

standard

UART

format

at

300

baud

(30

characters/second).

Marks

or

logic

ones

are

represented

by

recording

a

2400

Hz

sine

wave

on

the

tape

while

spaces

or.logic

zeroes

are

represented

by

re-

cording

a

1200

Hz

sine

wave.

With

the

proper

circuitry

this

recorded

data

can

then

be

read

off

the

tape

and

transposed

into

a

self

clocking

UART

based

tave

system

which

will

tolerate

audio

recorder

speed

variations

of

approximately

+30%.

This

figure

is

far

better

than

that:

of

most

other

modulation

techniques

and

is

a

real

advantage

when

you

consider:

the

degree

of

worst

case

speed

varia-

tion

between

inexpensive

audio

recorders.

In

addition

we

have

speed

variations

due

to

line

voltage,

battery

voltage,

wow

and

flutter,

mechanism

wear,

etc.

Thus

evolved

the

"Kansas

City"

standard.

It

should

be

noted

that

the

standard

does

not

specify

how

the

data

is

to

be

organized

on

the

tape,

so

there

can,

and

probably

will

be

some

incompatibility

among

various

manufact-

urer's

units.

This

is

however

more

of

a

software

problem

than

a

hardware

pro-

blem

and

thus

a

little

easier

to

resolve.

—

Although

the

SWTPC

AC-30

Audio

Cassette

Interface

has

been

used

extensive-

with

the

SWIPC

6800

Computer

System

and

CT-1024

(TV

Typewriter

II)

Terminal

‘Maitem,

it

has

been

designed

to

be

as

universal

and

flexible

a

system

as

pos-

sible.

If

your

computer's

control

terminal

is

interfaced

to

the

computer

thru

300

baud,

RS-232

compatible

serial

interfdces

with

accessible

UART

type

16

X

baud

rate

clocks

on

both

computer

and:

terminal,

the

SWTPC

AC-30

Cassette

Inter-

face

Unit

is

simply

plugged

between

the

computer

and

terminal

interfaces.

This

is

the

ideal

mode

of

operation

since

the

cassette

unit

can

take

full

advantage

ae

.

%

of

computer

resident

tape

load

and

dump::

youtines

and

requires

no

additional

interfaces,

Switching

the

cassette

unit.te

the

LOCAL

mode

directly

intercon-

:

nects

the

terminal

and

cassette

unit

for

‘Eerminal

'

‘only"

cassette

tape

operation

just

like

the

LOCAL

mode

of

operation

on.teletypewriters.

While

operating

in

the

REMOTE

mode

the

computer

communicattés

With

both

the

terminal

and

cassette

unit,

here

again

just

like

the

REMOTE

mode

of

operation

on

teletypewriters.

Those

customers

using

the

CT-1024

(TV

Typewriter

II)

Terminal

System

or

any

terminal

system

with

accessible

contrql.

‘character

decoders

may

even

pick

Reader

ON

(Control

Q),

Reader

OFF

(Control

S$),

Récerd.On

(Control

R),

and

Record

OFF

(Control

T)

control

commands

right

off

the

entrol

character

decoder

circuitry

on

their

terminal

system

giving

the

comptiter:

system

program

control

over

cas-~

sette

recorder

data

flow

and

even

motor

operation.

Those

not

having

access

to

decoded

control

commands

may

still

have”

gassette

control

by

driving

the

cas-

sette

interface

with

control

lines

from

a.geparate

parallel

interface

option

located

on

the

attached

computer

system.

a

These:

users

not

operating

their

connea?”

terminal

RS-232

serial

at

300

baud

or

hot

having

access

to

their

terminal's’

16.

X-

-UART

clock

may

still

use

the

cas-

sette

interface,

but

must

attach

it

to

thé

computer

system

thru

a

seperate

RS-232

serial

300

baud

interface

with

actédsible

16

X

clocks

located

on

the

computer

system.

This

however

eliminates’

thé

ability

to

use

the

computer

resi-

dent

control

terminal

tape

load

and

dump”

routines

as

well

as

the

LOCAL/REMOTE

feature

described

previously.

.

_

The

cassette

interface

circuitry

18’:

donsttacted

on

a

7

3/4"

X7

1/2"

double

sided,

plated

thru

hole

fibreglass

circuit

board

with

all

electrical

connections

made

to

the

board

thru

one

of

thi

five

edge

connectors.

The

three

connectors

along

the

back

edge

of

the

eirepit

board

are

for

connections

to

the

computer,

control

decoder

and

terminal

while

the

two

along

the

front

edge

are

for

connections

to

the

cassette

interface’

Si

eontrol

panel.

The

PC

board

in

turn

is

mounted

inside

a

12

3/4"

wide

X

3"?

high.

X

11"

deep

aluminum

chassis

with

dress

panel

and

perforated

cover.

PC

Board

Assembly

NOTE:

Since

all

of

the

holes

on

the

'PO-board

have

been

plated

thru,

it

is

only

necessary

to

solder

the:

components

from

the

bottom

side

of

the

board,

The

plating

provides

the

electrical

connectiaqn

-from.the

"BOTTOM"

to

the

"TOP"

foil

of

each

hole,

Unless

otherwise

noted

it.

is

important

that

none

of

the

connections

be

soldered

until

all

of

the

components

at

‘each

group

have been

installed

on

the

board.

This

makes

it

much

easier

to

interchange

components

if

a

mistake

is

made

during

assembly.

Be

sure

to

use

a

low

wattage

iron

(not

a

gun)

with

a

small

tip.

Do

not

use

acid

core

solder

or

any

type

of

paste

flux.

We

will

not

guarantee

or

repair

any

kit

on

which

either

product

has

‘been

used.

Use

only

the

solder

sup-

plied

with

the

kit

or

a

60/40 alloy

resin

“Core

.equivalent.

Remember

all

of

the

connections

are

soldered

on

the

bottom

side’

‘@£

‘the

board

only.

The

plated-thru

holes

provide

the

electrical

connection

to

bigs

8

Be

foil.

cong

aie

(

)

Before

installing

any

parts

on

the:

tedate’

board,

check

both

oo

of

the

board

over

carefully

for

incomplete

etching

and

foil

"bridges"

or

"breaks"

|

It

is

unlikely

that

you

will

find

any“but"

should

there

be

one

ee

\

on

the

"TOP"

side

of

the

board

it

will

“be*wery

hard

to

locate

and

correct

after

all

of

the

components

have

been

iptetted

on

the

board.

(

f

Attach

all

of

the

resistors

to

the

board.

As

with

all

other

components

unless

noted,

use

the

parts

list

and

component

layout

drawing

to

locate

each

part

and

install

from

the

"TOP"

side

of

the

board

bending

the

leads

along

the

"BOTTOM"

side

of

the

board

and

trimming

so

that

1/16"

to

1/8"

of

wire

remains.

Solder.

You

may

find

that

there

are

no

pads

on

the

"BOTTOM"

side

of

the

board

for

resistor

R42.

If

not

be

sure

its

two

leads

are

soldered

from

the

"TOP"

side

of

the

board.

(

)

Install

all

of

the

capacitors

on

the

board.

Be

sure

to

orient

the

electro-

lytic

capacitors

correctly.

The

polarity

is

indicated

on

the

component

layout

drawing.

The

body

of

electrolytic

capacitor

C21

should

be

insulated

so

as

not

to

"short"

to

foil

conductors

under

it.

If

the

body

of

the

cap-

acitor

is

not

insulated

attach

the

capacitor

so

it is

up

off

the

board

about

1/8".

Solder.

()

Starting

from

one

end

of

the

circuit

board

install

each

of

the

five

Molex

female

edge

connectors

along

the

edges

of

the

board.

These

connectors

must

be

inserted

from

the

"TOP"

side

of

the

board

and

must

be

pressed

down

firmly

against

the

board.

Make

sure

the

body

of

the

connector

seats

firmly

against

the

circuit

board

and

that

each

extends.

completely

into

the

holes

on

the

circuit

board.

()

Insert

the

small

nylon

indexing

plugs

into

the

edge

connector

pins

indi-

cated

by

the

small

triangular

arrows

on

the

"BOTTOM"

side

of

the

circuit

board.

This

prevents

mating

plugs

from

being

accidentally

plugged

onto

the

board

incorrectly.

(

)

Install

the

transistors

on

the

board.

The

transistors

must

be

turned

to

match

the

outlines

on

the

component

layout

drawing.

Solder.

( )

Install

all

of

the

diodes

on

the

board

excluding

diodes

D18

thru

D22.

The

diodes

must

be

turned

to

match

the

outlines

on

the

component

layout

draw-

ing.

Solder.

(

)

Install

LED

diode

D18

on

the

circuit

board.

Be

sure

the

flat

on

the

side

of

the

LED

matches

that

shown

on

the

component

layout

drawing.

Attach

the

diode

so

the

bottom

of

its

case

is

1/8"

to

1/4"

above

the

top

of

the

board.

Solder.

(

)

Install

reed

relays

RLY1

and

RLY2

on

the

circuit

board.

These

relays

are

not

polarized

so

they

need

not

be

oriented

in

any

particular

position

other

than

matching

the

end

with

three leads

and

the

one

with

just

one

to

the

respective

holes

on

the

circuit

board.

Solder.

()

Install

integrated

circuit

IC16

on

the

circuit

board.

This

component

must

be

oriented

so

its

metal

face

is

facing

the

circuit

board.

The

IC

is

se-

cured

to

the

circuit

board

with

a

#4-40

X

1/4"

screw,

lockwasher

and

nut.

The

three leads

of

the

integrated

circuit

must

be

bent

down

into

each

of

their

respective

holes

and

trimmed.

Solder.

NOTE:

Most

of

the

integrated

circuits

used

in

this

kit

are

CMOS

and

are

sus-

ceptable

to

damage

by

static

electricity.

Although

some

degree

of

protection

is

provided

internally

within

the

integrated

circuits,

their

sensitivity

de-

‘mands

the

utmost

in

care.

Before

opening

and/or

installing

any

CMOS

integrated

circuits

you

should

ground

your

body

and

all

metallic

tools

coming

into

contact

with

the

leads,

thru

a

1

M

ohm

1/4

watt

resistor

(supplied

with

the

kit).

The

ee

ground

must

be

an

"earth"

ground

such

as

a

water

pipe,

and

not

the

circuit

bord

ground.

As

for the

connection

to

your

body,

attach

a

clip

lead

to

your

watch

or

metal

ID

bracelet.

Make

absolutely

sure

you

have

the

1

Meg

ohm

resistor

con-

‘

nected

between

you

and

the

"earth"

ground,

otherwise

you

will

be

creating

a

dan-

gerous

shock

hazard.

Avoid

touching

the

leads

of

th?

integrated

circuits

any

more

than

necessary

when

installing

them,

even

if

you

are

grounded.

On

those

MOS

IC's

being

soldered

in

place;

the

tip

of

the

soldering

iron

should

be

grounded

as

well

(separately

from

your

body

ground)

either

with

or

wi-:hout

a

1

Meg

ohm

resistor.

Most

soldering

irons

having

a

three

prong

line

cord

plug

already

have

a

grounded

tip.

Static

electricity

should

be

an

important

consideration

in

cold,

dry

en-

vironments.

It

is

less

of

a

problem

when

it is

warm

and

humid.

()

Install

integrated

circuits

ICl

thru

IC15

following

the

precautions

given

in

the

preceding

section.

As

each

is

installed,

make

sure

it

is

down

firmly

against

the

board

before

soldering

all

of

its

leads.

Be

very

careful

to

install

each

in

its

correct

position.

Do

not

bend

the

leads

on

the

back

side

of

the

board.

Doing

so

makes

it

very

difficult

to

remove

the

inte-

grated

circuits

should

replacement

ever

be

necessary.

The

"dot"

on

the

end

of

the

package

is

used

for

orientation

purposes

and

must

match

with

that

shown

on

the

component

layout

drawing

for

each

of

the

IC's.

()

Working

from

the

"TOP"

side

of

the

circuit

board,

fill

in

all

of

the

feed-thru's

with

molten

solder.

The

feed-thru's

are

those

unused

holes

on

the

board

whose

internal

plating

connects

the

"TOP"

and

"BOTTOM"

circuit

connections.

Filling

these

feed-thru's

with

molten

solder

guaran-

tees

the

integrity

of

the

connections

and

increases

the

current

handling

capability.

()

Now

that

most

of

the

components

have

been

installed

on

the

board,

double

check

to

make

sure

all

have been

installed

correctly

in

their

proper

location.

()

Check

very

carefully

to

make

sure

that

all

connections

have

been

soldered.

It

is

very

easy

to

miss

some

connections

when

soldering

which

can

really

cause

some

hard

to

find

problems

later

during

check

out.

Also

look

for

solder

"bridges"

and

"cold"

solder

joints

which

are

another

common

problem.

Since

the

circuit

board

now

contains

CMOS

devices

it

is

susceptable

to

dam-

age

from

severe

static

electrical

sources.

One

should

avoid

handling

the

board

any

more

than

necessary

and

when

you

must,

avoid

touching

or

allowing

anything

to

come

into

contact

with

any

of

the

conductors

on

the

board.

Parts

List

AC-30 Audio

Cassette

Interface

Resistors

Rl

:

;

33K

ohm

1/4

watt

resistor

R2,

R3,

R9,

R11,

R12,

R15

10K

ohm

1/4

watt

resistor

R19+R22,

R27-R29, R32-R34,

:

10K

ohm

1/4

watt

resistor

R36,

.R40-R42,

R44-R47

10K

ohm

1/4

watt

resistor

R4,

R48,

R49

ot

330

ohm

1/4

watt

resistor

R5

2.2K

ohm

1/4

watt

resistor

R6

4.7K

ohm

1/4

watt

resistor

R7,

R30,

R31,

R35,

R37,

R43

470

ohm

1/4

watt

resistor

R8,

R17,

R18,

R23-R26

100K

ohm

1/4

watt

resistor

R1O

330K

ohm

1/4

watt

resistor

R13,

R14 22K

ohm

1/4

watt

resistor

R16

20K

ohm

trimmer

resistor

R38

47K

ohm

1/4

watt

resistor

R39

200K

ohm

trimmer

resistor

Capacitors

Cl,

C6,

C12-C15

1000

pfd

capacitor

C2

2000

pfd

capacitor

C3,

c8

0.022

mfd

capacitor

c4

;

1

mfd

@15

VDC

electrolytic

capacitor

C5,

C18

0,01

mfd

capacitor

C7,

C9

0.047

mfd

capacitor

C10

2700

pfd

capacitor

Cll,

C19,

C20

470

pfd

capacitor

C16,

C22

100

mfd

@16

VDC

electrolytic

capacitor

C17

10

mfd

@10

VDC

tantalum

capacitor

C2)

1000

mfd

@25

VDC

electrolytic

capacitor

C23-C€25

0.1

mfd

disc

capacitor

Semiconductors

Icl,

IC5,

IC8

4013

dual

D

flip-flop

Ic2,

ICll

4001

quad

NOR

gate

1c3,

IC13 4070

quad

EX-OR

gate

Ic4

4558

dual

op

amp

;

1c6,

IC14

:

4053

triple

multiplexer

1c7

4049

hex

buffer

Ic9

4023

triple

3-input

NAND

gate

Ic10

555

timer

1c12

1489

quad

RS-232

receiver

Ic15

1488

quad

RS-232

transmitter

IC16

7805

5

VDC

regulator

D1,

D2,

D4,

DS5-D11

1N4148

silicon

diode

D3

4.7

volt

zener

diode

1N4732

or

1N5230

D12,

D13

7.5

volt

zener

diode

1N4737

or

1N5236

D14-D17

1N4003

silicon

rectifier

D18-D22

light

emitting

diode

QI, Q2,

Q4-Q8_..

:

2N5210.

NPN

transistor

Q3,

Q9-Ql1

2N5087

PNP

transistor

Misc,

RLY1,

RLY2

6

VDC

reed

relay

$1-s3

;

-»

DPDT

miniature

toggle

switch

s4,

$5

:

Ms

:

;

SPDT

center

off

miniature

toggle

switch

$6,

S7

tes

=

h

*.

SPDT

miniature

toggle

switch

Tl

a

=

.

18

VAC

@300

Ma.

secondary

120/240

VAC

:

ve

a

50-60

Hz

primary

power

transformer

Fl

:

‘1

amp

standard

fuse

Chassis

Assembly

Sandwich

the

dress

panel

between

the

chassis

and

mounting

hardware

and

attach

switches

S1-S7

to

the

chassis

using

the

wiring

pictorial

to

show

proper

loc-

ation

and

orientation.

Secure

each

switch

using

a

finishing

washer

and

nut.

Insert

each

of

the

four

LED

plastic

mounting

clips

into

the

front

panel

holes

provided

for

LED

diodes

D19

thru

D22.

Insert

each

of

the

LED

diodes

into

the

clips

so

that

the

flat

on

the

side

of

each

diode

matches

with

that

shown

in

the

wiring

pictorial.

Just

for

reference

the

side

with

the

flat

is

the

same

as

the

side

with

the

shorter

lead.

Secure

each

LED

diode

with

the

plastic

retaining

ring.

This

ring

must

be

pressed

on

tightly

to

prevent

the

LED

from

being

loose.

Attach

RCA

jacks

J6

thru

J9

to

the

chassis.

Jack

J6

should

have

a

ground

lug

put

under

it.

Secure

each

jack

with

a

1/4"

nut.

RCA

jacks

J10

and J1l

must

be

electrically

insulated

from

the

chassis.

In

order

to

do

this,

first

slip

a

shoulder

washer

over

each

RCA

jack

with

the

shoulder

against

the

inside

of

the

chassis,

place

the

jack

against

the

out-

side

of

the

chassis,

put

another

shoulder

washer

on

the

back

side

of

the

jack

with

the

shoulder

against

the

inside

of

the

chassis,

follow

this

with

the

ground

lug

and

finally

secure

with

a

1/4"

nut.

Attach

the

power

transformer

to

the

chassis

using

#6-32

X

1/4"

screws,

lock-

washers

and

nuts.

Orient

the

transformer

so

the

end

with

the

three

wires

coming

out

of

it

is

toward

the

front

of

the

chassis.

Attach

the

fuseholder

to

the

chassis

using

a

#6-32

X

3/8"

screw,

lockwasher

and

nut.

Snap

the

four

nylon

PC

board

supports

into

the

holes

provided

for

them

in

the

chassis.

eee

Snap

the

1

1/2"

bushing

into

the

large

hole

provided

on

the

back

of

the

chassis.

The

bushing

should

be

installed

from

the

outside

of

the

chassis.

Turn

the

chassis

upside

down

and

attach

each

of

the

four

press

on

rubber

feet

about

1"

in

from

each

of

the

corners.

Using

a

pair

of

pliers,

crimp

the

strain

relief

onto

the

line cord

at

a

‘point

12"

from

the

end

of

the

cord.

While

compressing

the

strain

relief

insert

the

12"

length

of

the

line

cord

and

the

strain

relief

into

the

7/16"

hole

provided

on

the

back

of

the

chassis,

from

the

outside

of

the

chassis.

Press

the

specified

color

of

switch

cap

onto

the

handle

of

each

toggle

switch

as

specified

below:

;

Sl

-

white

f

$2

-

green

$3

-

green

S84

-

yellow

$5

-

yellow

S6

-

red

S7

-

white

ey ee

()

Snap

the

ten

tinnerman

clips

onto

the

holes

provided

on

the

front

and

back

lips

of

the

chassis.

Chassis

Wiring

All

connections

made

between

the

components

on

the

chassis

and

the

printed

circuit

board

are

made

thru

connectors

Jl

and

J2.

This

allows

one

to

easily

remove

the

PC

board

for

service

or

access

to

the

bottom

side

of

the

PC

board.

When

soldering

the

wires

to

the

main

plugs

for

connectors

Jl

and

J2,

the

plugs

must

not

be

plugged

into

the

PC

board.

If

they

are

the

female

connect-

ors

may

melt

and

be

ruined.

Follow

the

wiring

steps

outlined

on

the

pages.

Note

for

220

VAC

Operation

-

To

wire

the

unit

for 220

VAC

operation,

omit

wiring

steps

1

thru

4

and

instead

solder

together

and

insulate

Tl's

Black-

White

and

Black

leads.

Then

connect

Tl's

White

wire

to

Fl

terminal

A

and

solder.

Also

connect

Tl's

Red-Black

wire

to

S6

terminal

A

and

solder.

Plug

connectors

Jl

and

J2

to

the

appropiate

jacks

on

the

PC

board.

Be

sure

to

orient

the

jacks

correctly.

Bundle

any

loose

wires

with

the

wire

ties

supplied

with

the

kit.

Snap

the

PC

board

into

place.

AC-=30

Wiring

Table

WIRE

FROM

a

Pe

ee

fe

se

a

aoe

ari

a

wauaL

NOTOR

VER]

ves

ton

“continued

on

a

Switches,

Indicators

&

Jacks

The

complement

of

front

panel

switches,

indicators

and

jacks

includes

the

following:

MIC,

EAR

and

REMOTE

jacks

for

recorder

A:

These

jacks

should

be

con-

nected

thru

patch

cords

to

the

cassette

recorder's

respective

jacks.

It

is

often

times

necessary

to

patch

the

MIC

output

of

the

cassette

interface

to

the

AUX

input

rather

than

the

MIC

input

of

the

recorder

to

be

used.

Some

experimentation

may

be

necessary

here.

Be

sure

the

cassette

recorder(s)

you

select

have

a

REMOTE

jack

on

them.

This

is

necessary

in

order

to

have

cassette

recorder

motor

control.

MIC,

EAR

and

REMOTE

jacks

for

recorder

B:

These

jacks

may

be

used

for

feeding

a

second

cassette

recorder

often

required

when

using

Editor/

Assembler

software

packages.

Their

functional

description

is

ident-

ical

to

that

provided

for

recorder

A.

RECORD

SELECT

A/B:

When

this

two

position

switch

is

in

the

A

position,

the

cassette

interface

will-

output

all

record

data

to

cassette

record-

er

A.

When

in

the

B

position

it

will

output

all

record

data

to

cas-

sette

recorder

B.

READ

SELECT

A/B:

When

this

two

position

switch

is

in

the

A

position,

the

cassette

interface

will

input

all

read

data

from

cassette

record-

er

A.

When

in

the

B

position

it

will

input

all

read

data from

cas-

sette

recorder

B.

RECORD

STATUS

ON/OFF:

This

three

position

switch

is

normally

left

in

the

center

position

allowing

computer

program

generated

control

com-

mands

to

set

the

state

of

the

record

latch.

Momentarily

flipping

the

switch

to

the

ON

or

OFF

position

will

manually

update

the

status

of

the

record

latch.

Leaving

the

switch

in

either

the

ON

or

OFF

position

will

override

computer

program

control

entirely.

A

ccrvenient

LED

status

indicator

just

to

the

left

of

this

switch

always

shows

the

state

of

the

record

latch.

The

operation

of

the

cassette

interface

as

a

function

of

the

state

of

the

record

latch

is

dependent

upon

the

set-

ting

of

the

motor

control

switch

which

is

described

in

detail

later.

READ

STATUS

ON/OFF:

This

three

position

switch

is

normally

left

in

the

center

position

allowing

computer

program

generated

control

com-

mands

to

set

the

state

of

the

read

latch.

Momentarily

flipping

the

switch

to

the

ON

or

OFF

position

will

manually

update

the

status

of

the

read

latch.

Leaving

the

switch

in

either

the

ON

or

OFF

position

will

override

computer

programcontrol

entirely.

A

convenient

LED

status

indicator

just

to

the

left

of

the

switch

always

shows

the

state

of

the

read

latch.

The

operation

of

the

cassette

interface

as

a

fun-

ction

of

the

state

of

the

read

latch

is

dependent

upon

the

setting

of

the

motor

control

switch

which

is

described

in

detail

later.

RECORD

DATA

INDICATOR:

This

LED

indicator

shows

the

transmission

of

valid

record

data

out

of

the

cassette

interface.

It

lights

only

when

the

record

latch

is

on

and

logic

zeros

or

spaces

are

being

transmitted.

This

allows

the

operator

to

confirm

that

a

tape

dump

is

in

progress

when

lit

since

the

null

data

marking

output

does

not

light

the

indicator.

a

Be

READ

DATA

INDICATOR:

This

LED

indicator

shows

the

receipt

of

valid

read data

into

the

cassette

interface.

It

lights

only

when

the

read

latch

is

on,

valid

FSK

data

is

detected

on

the

tape

and

logic

zeros

or

spaces

are

being

received.

This

allows

the

operator

to

confirm

that

a

tape

load

is

in

progress

when

lit

since

the

null data

marking

input

or

a

loss

of

audio

tones

does

not

light

the

indicator.

MOTOR

CONTROL

-

MANUAL/AUTO:

The

position

of

the

motor

control

switch

actually

determines

the

function

of

the

record

and

read

status

latches.

In

the

MANUAL

position

both

the

record

and

read

cassette

recorder

mo-

tors

are

always

activated

thru

their

respective

REMOTE

jacks.

If

the

record

latch

is

off,

the

interface's

selected

recorder

MIC

jack

will

output

a

constant

marking

carrier,

even

if

there

is

data

flowing

back

and

forth

between

the

computer

and

terminal.

As

soon

as

the

record

latch

is

turned

on

either

by

the

computer

or

manual

control,

all

data

transmitted

from

the

computer

to

the

terminal

is

simultaneously

trans-

mitted

out

thru

this

same

MIC

jack.

Data

flow

out

of

the

MIC

jack

ceases

as

soon

as

the

record

latch

is

again

reset

by

either

manual

or

computer

control.

If

the

read

latch

is

off

the

interface

will

ignor

all

data

in-

coming

thru

its

selected

EAR

jack

and

yet

pass‘data

back

and

forth

between

the

terminal

and

computer.

If

the

read

latch

is

turned

ON

either

by

manual

or

computer

control

and

valid

audio

tones

are

sensed

from

the

selected

EAR

jack,

read

data

is

stored

from

the

cassette

unit

to

the

computer.

This

same

data

is

simultaneously

displayed

on

the

attached

terminal

system

only

if

the

computer

is

programmed

to

echo

the

incoming

cassette

data.

Data

flow

from

the

cassette

to

the

computer

system

ceases

either

upon

resetting

the

read

latch

or

loss

of

audio

tones

on

the

tape.

Operation

in

the

AUTO

position

is

quite

different.

If

both

the

record

and

read

latches

are

reset,

cassette

recorder

motor

operation

is

inhibited

thru

the

respective

REMOTE

jacks

on

both

the'record

and

read

recorders.

The

interface's

selected

record

MIC

jack

will

output

no

audio

data,

even

if

there

is

data

flowing

back

and

forth

between

the

computer

and

terminal.

As

soon

as

the

record

latch

is

turned

ON,

the

recording

recorder's

motor

is

turned

on

thru

the

respective

RE-

MOTE

jack

and

a

variable

delay

timer

is

fired

which

delays

the

output

of

audio

marking

data

to

allow

this

same

cassette

recorder's

tape

to

come

up

to

normal

tape

speed.

This

hardware

delay

circuit

must

be

supplemented

with

a

software

delay

loop

written

into

your

programs

to

guarantee

that

you

don't

start

outputting

record

data

until

after

this

hardware

delay

timer

on

the

cassette

interface

has

already

timed

out.

When

the

record

latch

is

again

turned

off,

the

interface

will

cease

to

output

audio

data

and

the

selected

recorder's

motor

is

turned

off.

Here

again

it

is

wise

to

include

a

software

delay

loop

in

your

programs

to

give

the

recorder

time

to

come

to

a

complete

stop,

This

guarantees

a

sufficient

gap

between

multiple

recorded

segments

to

allow

one

to

do

either

incremental

(start-stop)

or

continuous

reads

from

the

same

tape.

5

When

the

read

latch

is

turned

on

the

read

recorder's

motor

is

started.

The

interface

inhibits

all

read

recorder

data

until

valid

audio

tones

are

detected,

at

which

time

all

incoming

cassette

data

is

stored

to

the

computer

and

simultaneously

displayed

on

the

terminal

only

if

the

computer's

echo

is

enabled.

Reads

may

be

either

continuous

ae

or

incremental

(start-stop).

Since

incremental

tapes

have

blank

gaps

between

recorded

segments,

the

cassette

interface's

audio

tone

sensing

circuitry

has

been

designed

to

ignor

all

but the

valid

data

segments

stored

on

the

tape.

:

LOCAL/REMOTE

switch:

The

LOCAL/REMOTE

switch

on

this

cassette

inter-

face

is

analogous

to

that

on

standard

teletypewriters.

In

the

LOCAL

mode

there

is

a

direct

data

link

between

the

terminal

and

cassette

recorder(s).

The

computer

is

electrically

eliminated

from

the

system.

In

the

REMOTE

or

normal

mode

of

operation,

the

computer,

terminal

and

cassette

recorder(s)

are

all

linked

together.

POWER

ON/OFF:

This

switch

controls

AC

power

to

the

cassette

interface

unit.

It

must

be

powered

up

consistently

with

the

interconnected

com-

puter

and

terminal

systems

even

if

cassette

operation

is

not

desired.

Attaching

the

Interface

to

the

Recorders

If

you

will

be

using

the

interface

just

for

loading

and

storing

programs

and

data

files

to

and

from

tape

you

will

probably

need

jtist

one

cassette

recorder.

If

however,

you

will

be

doing

tape

file

editing

or

using

assembler

packages

you

will

probably

have

to

use

two

cassette

recorders.

The

same

single

interface

will

handle

both

configurations.

Electrical

connections

between

the

cassette

inter-

face

and

recorders

are

best

made

by

cutting

several

3'

to

4'

audio

patch

cords

with

the

molded

RCA

connectors

on

both

ends,

in

half

and

fitting

the

newly

cut

ends

with

the

appropiate

recorder

jack

mating

connectors.

Some

cassette

re-

corders:

such

as

the

ones

used

with

the

prototype

have

both

high

level

AUX

and

low

level

MIC

inputs.

In

our

case

it

was

necessary

to

use

the

AUX

input

since

the

cassette

recorder

circuitry

would

not

permit

the

reading

of

a

tape

with

a

plug

simultaneously

installed

in

the

MIC

jack.

Be

sure

to

use

a

cassette

re-

corder

featuring

an

AGC

(automatic

gain

control)

circuit.

Most

all

late

model

cassette

recorders

havethis

feature.

Since

cassette

motor

control

is

available

you

will

want

a

recorder

with

a

REMOTE

jack

that

stops

the

recorder's

motor.

Here

again

recorder

circuitry

varies.

Some

units

disable

just

the

motor

while

others

disable

everything.

It is

best

in

this

instance

to

just

disable

the

motor,

the

idea

being

to

minimize

the

recorded

transients

between

blocks

of

data

when

using

the

interface

in

the

incremental

(start~stop)

mode

of

recording.

The

recorders

used

with

the

prototype

were

Superscope\’/models

C-101A.

Al-

though

they

were

reliable,

close

examination

of

the

quality

of

recorded

data

with

an

oscillioscope

left

a

lot

to

be

desired.

The

optimum

volume

control

setting

was

around

7

on

a

scale

of

0

to

LO.

:

The

quality

of

the

cassette

tape

used

with

your

recorder(s)

will

also

af-

fect’

the

reliability

of

your

system.

Here

the

best rule

of

thumb

is

to

assume

you

get

what

you

pay

for.

The

most

expensive

tapes

will

generally

give

you

better

reliability.

Remember

too

that

you

are

recording

audio

frequency

data

not

saturated

pulses,

so

don't

use

digital

computer

grade

cassette

tapes.

Al~

ways

erase

previously

recorded

tapes

with

a

bulk

tape

eraser

such

as

a

Radio

Shack

#44-210

($9.95)

before

rerecording

them.

This

is

especially

important

when

using

the

system

in

the

incremental

(start-stop)

mode

of

operation.

Bulk

tape

erasers

generally

do

a

better

job

of

erasing

than

your

recorder's

internal

circuitry

and

guarantee

that

you

don't

pick

up

segments

of

previously

recorded

programs

or

data.

Superscope

is

a

registered

trademark

of

Superscope

Inc.

=

i

The

interface's

read

circuitry

must

be

calibrated

for

use

in

the

read

mode

before

using

the

interface.

This

is

best

done

by

using

your

computer

or

terminal

to

generate

a

calibration

tape

with

continuous

ASCII

5's

recorded

on

it

and

then

reading

back

the

tape

to

the

computer

in

the

REMOTE

mode

or

terminal

in

the

LOCAL

mode

while

adjusting

trimmer

resistor

R16

for

a

center

setting between

errored

reads.

ASCII

fives

have

an

alternating

bit

sequence

ideal

for

calibration.

It

is

a

goodidea

to

periodically

recheck

this

setting

using

your

previously

generated

calibration

tape.

:

Before

using

your

cassette

interface

unit

in

the

incremental

(start-stop)

mode

of

recording

it

will

be

necessary

to

set

the

time

delay

on

the

carrier

enable

one

shot,

trimmer

resistor

R39,

so

as

to

allow

the

recorder's

motors

to

come

up

to

speed

before

outputting

a

marking

audio

tone.

This

is

best

done

by

visually

measuring

your

recorder's

motor

start

time

and

then

multiplying

by

two

just

for

a

safety

factor.

The

interface's

delay

is

then

set

by

adjusting

trimmer

resistor

R39

for

this

same

time

delay

between

the

time

the

RECORD

"READY"

indicator

lights

and

the

CARRIER

ENABLED

indicator

(LED

diode

D18)

comes

on.

The

latter

is

mounted

right

on

the

interface's

PC

board

adjacent

trimmer

resistor

R39.

Whenever

you

are

writing

to

tape

in

the

incremental

(start-stop)

mode

you

must

provide

a

software

delay

loop

in

your

program

that

is

at

least-as

long

as

the

adjustable

hardware

timer

delay

plus

0.5

seconds.

The

additional

half

second

is

required

to

guarantee

a

carrier

detect

signal

before

data

flow

when

the

tape

is

being

read.

It

is

also

a

good

idea

to

put

a

header

character

or

characters

at

the

beginning

of

each

incremental

record.

Upon

reading

these

records,

your

program

should

be

written

such

that

it

ignors

all

data

between

these

recorded

segments

until

this

header

data

is

read.’

The

cassette

inter-

face

is

more

vulnurable

to

error

reads

between

incrementally

recorded

data

than

at

any

other

time.

The

end

of

each

data

block

may

easily

be

detected

by

re-

cording

some

non-displayed

control

character

at

the

end

of

each

data

block.

If

you

are

using

the

cassette

interface

with

the

SWIPC

6800

Computer

system

and

CT-1024

(TV

Typewriter

II)

terminal

system,

the

decoded

RECORD

OFF

ASCII

Control

T

command

(1416)

not

only

turns

the

recorder

off

but

is

written

at

the

end

of

the

data

record

as

well,

for

an

end-of-record

character.

Incrementally

recorded

records

may

be

read

either

continuously

or

incremen-

tally.

In

either

case

you

must

provide

a

software

delay

in

your

program

at

least

one

character

time

(33

milliseconds)

between

the

time

the

end-of-record

character

is

read

and

the

time

data

is

output

from

the

interface.

The

reason

being

that

there

is

a

slight

delay

between

the

loss

of

carrier

on

the

tape

and

action

of

the

CARRIER

DETECT

circuitry

which

in

turn

creates

a

gap

in

the

16

X

UART

clock.

This

gap

causes

no

problems

so

long

as

you

are

not

outputting

data

during

the

clock

gap

thus

the

reason

for

the

delay.

Fortunately

all

of

the

formentioned

considerations

are

only

necessary

when

using

the

interface

in

the

incremental

(start-stop)

mode.

Operating

the

system

in

the

continuous

(motor

control

disabled)

mode

isn't

much

different

from

paper

tape

operation.

You

will

of

course

have

to

manually

start

and

stop

the

record-

ers

but

no

special

recording

considerations

are

necessary

which

usually

allows

use

of

unmodified

computer

resident

tape

load

and

dump

routines

for

program

storing

and

loading.

a

1g

=

Interfacing

to

a

SWIPC

5800

and

C7-!924

Terminal

Svstem

As

mentioned

earlier

the

ideal

configuration

for

using

the

AC-30

Audio.

-Cas-

sette

Interface

is

with

the

SwWTPC

6800

Computer

System

and

CT-1024

Terminal

Sy-

stem.

The

Terminal

system

must

be

outfitted

with

the

CT-S

Serial

Interface

along

with

the

CT-SO

optional

baud

rate

kit.

For

those

not

already

having

the

baud

op-

tion,

we

now

offer

the

optional

baud

rate

kit

for

$14.75

PPd,

in

the

U.S.

The

terminal

and

computer

must

be

operated

at

300

baud.

The

terminal

system

must

also

be

outfitted

with

the

CT-CA

Computer

Controlled

Cursor

Option,

This

board

is

nec-

essary

to

generate

the

decoded

control

commands

which

are

fed

to

the

AC-30

Cas-

sette

Interface.

Electrically

the

AC-30

Cassette

Interface

is

plugged

in

series

between

the

6800

and

the

CT-1024.

You

simply

remove

the

plug

connecting

the

CT-1024

Ter-

minal

System

to

the

computer's

control

interface

and

plug

it

into

the

AC-30

in-

stead.

A

separate

connector

then

connects

the

AC-30

Cassette

Interface

to

the

MP-C

Control

Interface

on

the

Computer

Svstem:

The

computer's

MP-C

Control

In-

terface

must

be

jumpered

for

300

baud

operation.

In

this

configuration

all

data

passing

between

the

computer

and

terminal

may

if

selected

be

written

to

tape

or

‘supplemented

with

data

from

tape.

Connections

from

the

CT-1024

Terminal

System's

CT-S

Serial

Interface

16X

baud

rate

clock

and

CT-CA

Computer

Controlled

Cursor

decoded

control command

logic

are

made

to

the

AC-30

Cassette

Interface

thru

the

center

connector

on

the

back

of

the

AC-30

circuit

board.

The

SWIPC

6800/CT-1024

Interconnection

Drawing

shows

all

connections

that

need

be

made

for

this

configuration.

The

AC-30

Cassette

Interface

must

always

be

powered

up

when

using

the

system

even

if

vou

are

not

using

a

cassette

tape

since

all

computer/terminal

data

flow

is

thru

the

cassette

interface.

After

attaching

the

supplied

connector

to

the

CT-1024

Terminal

System

vou

should

note

that

the

16X

clock

for

the

CT-S

Serial

Interface

was

broken

when

installing

the

cassette

connector,

This

brake

prevents

the

CT-1024

Terminal

System

from

oper-

ating

if

it

is

not

attached

to

the

AC-30

Cassette

Interface.

For

this

reason

the

connections

for

a

dummy

plug

have

been

shown

which

must

be

plugged

onto

the

CT-1024

Terminal

System's

connector

for

stand-alone

operation.

so

don't

forget

to

install

the

dummy

plug

on

the

terminal's

connector

when

using

the

terminal

system

without

the

AC-30

Cassette

Interface,

After

actually

interconnecting

the

AC~30

with

your

system

flip

the

LOCAL/

REMOTE

switch

to

the

REMOTE

position

and

you

should

find

that

you

have

normal

communication

with

the

computer

system.

If

vou

flip

the

same

switch

to

the

LOCAL

position

you

should

find

that

everything

typed

on

the

terminal's

keyboard

is

echoed

to

the

terminal's

screen,

even

though

the

ECHO

ON/OFF

switch

on

the

keyboard

18

in

the

OFF

position.

Before

you

actually

try

to

load

or

store

a

program

on

tape,

the

unit

must

be

calibrated

using

the

FIVPNT-1

Interface

Cal-

ibration

Program.

A

copy

of

this

program

is

contained

within

a

seperate

section

of

this

instruction

set,

It

might

also

be

wise

to

run

the

other

diagnostic

pro-

grams

which

are

also

contained

within

this

instruction

set.

When

you

are

run-

ning

the

diagnostic

programs

you

mav

find

that

the

terminal

will

occasionally

omit

a

character

when

reading

a

tape

back

in

the

LOCAL

mode.

This

as

we

found

is

a

problem

in

the

terminal

and

not

in

the

AC-30

Cassette

Interface.

If

you

wish

to

correct

the

problem

carefully

separate

1

of

IC3l

on

the

CT-1024

Terminal

System

from

its

connection

to

the

circuit

board.

Attach

and

solder

a

wire.

from

this

now

isolated

to

1C26

13,

It

is

a

good

idea

to

increase

the

value

of

C4

on

the

CT-CA

board

on

the

CT-1024

Terminal

System

from

a

100

pfd

capacitor

to

a

1000

pfd

capacitor.

You

may

also

find

when

vou

are

reading

back

tapes

recorded

in

the

incremental

mode

that

question

marks

occasionally

‘show

up

between

incrementally

recorded

records.

This

is

where

the

AC-30

is

most

2

PS,

te

vulnerable

to

errored

reads

and

is

best

solved

by

your

putting

a

header

charac-

.

ter(s)

at

the

beginning

of

each

incrementally

recorded

record

as

the

Editor/As-

sembler

programs

do.

Header

characters

have

not

been

used

in

the

diagnostics

so

that

the

user

may

see

all

non-control

character

data

written

to

tape.

Some

experimentation

with

volume

control

settings

will

probably

be

neces-

sary.

Run

the

diagnostics

at

various

volume

control

settings

and

choose

the

one

that

gives

you

the

most

reliable

results.

Let's

assume

now

we

have

a

SWIPC

6800

Computer

and

CT-1024

Terminal

System

interfaced

together

with

300

baud

RS-232

serial

interfaces.

As

mentioned

earli-

er

for

this

configuration,

the

cassette

interface

is

connected

in

series

between

the

two

taking

full

advantage

of

the

computer's

firmware resident

tape

dump

and

load

routines.

Let's

assume

we

have

a

program

we

wish

to

dump

to

tape

which

is

already

stored

in

the

computer's

memory

with

the

computer's

pro-

gram

counter,

storage

addresses

(A#48

and

Af49),

set

to

the

starting

location

of

the

program.

Now

use

the

memory

change

function

to

set

the

starting

and

ending

addresses

of

the

memory

segment

to

be

dumped

in

locations

AM@2

thru

AP5.

The

cassette

interface's

switches

should

be

set

for

manual

motor

control

with

the

RECORD/READ

status

switches

in

the

center

position

and

the

LOCAL/REMOTE

switch

in

the

REMOTE

position.

Load

a

blank

or

previously

erased

tape

into

the

selected

cassette

recorder

and

depress

the

REWIND

button

to

get

to

the

beginning

of

the

tape.

Then

depress

the

PLAY

button

to

advance

several

seconds

beyond

the

leader

on

the

tape.

Stop

the

recorder

and

this

time

depress

the

cassette

record-

er

RECORD

button.

Then

enter

a

P

for

punch

on

the

terminal's

keyboard.

The

record

STATUS

light

will

come

on

and

the

record

DATA

light

will

flicker

as

pro-

gram

data

is

stored

to

the

cassette

tape.

When

the

dump

is

completed

both

the

STATUS

and

DATA

lights

will

go

out.

Do

not

stop

the

recorder,

instead

set

mem—

ory

locations

A##2

thru

A#@5

to

dump

the

data

stored

in

the

program

counter

storage

addresses

as

well.

Since

the

record

STATUS

light

is

not

lit,

none

of

this data

passing

back

and

forth

between

the

terminal

and

computer

is

written

to

the

still

operating

recorder.

Again

enter

a

P

for

punch.

The

STATUS

and

DATA

lights

will

again

come

on,

but

only

for

a

fraction

of

a

second

since

only

two

memeory

locations

are

written

to

the

tape.

Now

while

the

cassette

recorder

is

still

recording

flip

the

LOCAL/REMOTE

switch

to

the

LOCAL

position,

use

the

manual

RECORD

status

switch

to

set

the

record STATUS

latch

and

type

in

on

the

terminal's

keyboard

S9.

Reset

the

RECORD

status

latch

to

the

off

position

and

stop

the.

recorder.

Don't

forget

to

flip

the

LOCAL/REMOTE

switch

back

to

the

normal

REMOTE

position.

Before

trying

to

load

this

same

program

you

might

want

to

momentarily

turn

the

computer

off

just

to

make

sure

the

memory

resident

program

is

destroyed

before

loading.

eapplying

power

will

force

an

auto-reset

and

bring

up

the

resident

MIKBUG

firmware

on

the

SWIPC

6800.

Rewind

the

tape

to

the

beginning,

make

sure

the

cassette

recorder's

volume

is

set

to

a

reliable

setting

and

de-

press

the

play

button.

Then

type

in

a

L

for

load

on

the

terminal's

keyboard.

The

read

STATUS

light

will

immediately

come

on

since

the

firmware

outputs

a

READ

ON

control

command.

The

DATA

light

however

will

remain

off

until

program

data

is

detected

on

the

tape

at

which

time

it

will

begin

to

flicker.

When

it

stops

flickering

it

means

that

the

program

data

has

been

loaded

to

the

computer's

memory

but

don't

forget

that

the

program

counter

data

was

also

written

to

the

tape

so

the

is

that

of

the

program

counter

being

loaded.

A

S9

was

also

written

to

the

tape

which

is

an

end

of

tape

marker.

Upon

reading

this

the

computer

will

output

a

READ

OFF

control

command

forcing

the

read

STATUS

light

to

go

out

hence

ignoring

all

subsequent

data

stored

on

the

tape

should

the

recorder

be

left

to

run.

The

program

as

well

as

the

program

counter

have

been

loaded.

Simply

typing

in

the

character

"G"

for

go

should

initiate

the

program.

mrkpuc(®)is

a

registered

trademark

of

Motorola

Inc.

es

ee

Interfacing

to

a

SWIPC

6800

and

non-CT-1024

300

Baud

Terminal

System

The

terminal

used

must

be

a

300

baud

RS-232

terminal

as

is

the

CT-1024

Ter-

minal

System.

It

is

desirable

that

the

terminal

have

an

accessible

16X

baud

rate

clock.

If

not

it is

still

usable

but

you

will

not

be

guaranteed

of

reliable

tape

reads

when

reading

tapes

in

the

LOCAL

mode.

You

will

also

not

be

able

to

record:

tapes

directly

from

the

terminal

in

the

LOCAL

mode

since

the

AC-30

logic

requires

the

terminal's

16X

baud

rate

clock

for

recording.

If

your

terminal

does

not

have

control

character

decode

circuitry

you

may

still

load

programs

but

without

soft-

ware

control.

The

Editor/Assembler

software

package

requires

motor

control

and

for

this

reason

has

motor

control

logic

fed

out

of

unused

lines

on

the

MP-C

Con-

trol

Interface

board.

This

means

that

you

can

derive

the

cassette

logic

control

for

the

AC-30

Cassette

Interface

from

a

connector

installed

on

the

MP-C

Control

Interface

board.

This

cassette

control

logic

is

only

functional

when

the

Editor/

Assembler

software

is

resident

and

will

not

operate

with

the

MIKBUG

R

firmware

or

other

software

packages

unless

the

appropiate

driving

software

has

been

writ-

ten

into

them.

Since

MIKBUG

is

tolerent

of

non-program

data

encountered

when

loading

tapes

we

may

fortunately

still

load’

and

store

programs

without

cassette

logic

control.

If

by

chance

your

terminal

does

have

control

character

decode

circuitry

it

is

unlikely

its

timing

arid

phasing

are

the

same

as

that

of

the

CT-CA

board

on

the

CT-1024

Terminal

System.

The

Reader

ON,

Reader

OFF,

Record

ON

and

Record

OFF

control

lines

should

be

TTL

compatible

pulses

between

1

and

1000

microseconds

duration.

The

logic

is

set

up

for

negative

going

pulses,

however,

grounding

the

CONTROL

INVERT

line

on

the

AC-30

board

programs

the

AC-30

for

posi-

tive

going

pulses.

If

you

are

forced

to

use

the

cassette

control

logic

put

out

on

the

SWIPC

6800's

MP-C

Control

Interface

board

by

the

Editor/Assembler

software,

make

the

following

connections

from

the

indicated

pins

of

ICl

on

the

MP-C

Control

Inter-

face

board

to

the

specified

pins

of

a

twelve

male

connector

shell.

Be

sure

to

make

the

wires

long

enough

to

reach

your

AC-30

Cassette

Interface

where

‘the

connector

will

be

plugged.

If

you

do

have

access

to

your

terminal's

16X

baud

rate

clock,

the

terminal's

clock

buss

should

be

broken

and

the

16X

clock

OUT

and

16X

clock

IN

lines

brought

out

to

the

same

connector:

FROM

TO

MP-C

ICl

7

12

male

shell

female

#1

MP-C

ICl

4

12

male

shell

female

#2

MP-C

ICl

6

12

male

shell

female

#3

MP-C

ICL

5

12

male

shell

female

#4

Terminal's

16X

clock

OUT

12

male

shell

female

#5

Terminal's

16X

clock

IN

12

male

shell

female

#6

MP-C

ground

12

male

shell

female

#12

The

mating

connector

on

the

AC-30

Cassette

Interface

as

well

as

other

in-

terconnections

to

the

unit

should

be

installed

just

as

it

is

shown

in

the

inter-

connection

drawing

for

the

SWTPC

6800

and

CT-1024

Terminal

System,

Let's

assume

now

that

we

have

a

SWTPC

6800

Computer

System,

AC-30

Cassette

Interface

and

300

baud

terminal

system

and

are

taking

cassette

control

commands

off

the

MP-C

Control

Interface

on

the

SWIPC

6800

Computer

System,

Although

the

AC-30

Cassette

Interface

is

in

series

between

the

computer

and

terminal

systems

we

have

no

means

of

getting

the

cassette

control

commands

to

the

cassette

inter-

face

since

the

MIKBUG

R

¢irmware

does

not

generate

cassette

control

commands

on

the

MP-C

Control

Interface

board.

Once

the

Editor/Assembler

program

has

been

at

loaded

the

input/output

routines

within

the

package provide

the

necessary

casset—

te

control

commands

required

for

the

software

motor

control

mode

of

operation

of

the

package.

You

do

not

have

to

have

cassette

control

logic

to

simply

load

and

store

programs

with

the

AC-30

Cassette

Interface

although

it

is

easier

to

use

if

you

do.

Let's

assume

now

we

have

a

program

we

wish

to

dump

to

tape

which

is

already

stored

in

the

computer's

memory

with

the

computer's

program

counter,

storage

ad-

dresses

(AQ48

and

A#49),

set

to

the

starting

location

of

the

program.

Now

use

the

memroy

change

function

to

set

the

starting

and

ending

addresses

of

the

memory

segment

to

be

dumped

in

locations

Aff2

thru

A##5.

The

cassette

interface's

switches

should

be

set

for

manual

motor

control

with

the

RECORD/READ

status

switches

in

the

center

position

with

the

status

lights

out

and

the

LOCAL/

REMOTE

switch

in

the

REMOTE

position.

Load

a

blank

or

previously

erased

tape

into

the

selected

cassette

recorder

and

depress

the

REWIND

button

to

get

to

the

beginning

of

the

tape.

Then

depress

the

PLAY

button

to

advance

several

seconds

beygnd

the

leader

on

the

tape.

Stop

the

recorder

and

this

time

depress

the

cassette

yecord-

er

RECORD

button.

Flip

the

RECORD

status

switch

to

set

the

RECORD

status

light

ON.

Then

enter

a

P

for

punch

on

the

terminal's

keyboard.

The

record

DATA

light

will

flicker

as

program

data

is

stored

to

the

casset-

te-tape.

When

the

dump

is

completed

the

DATA

light

will-go

out.

Do

not

stop

the

recorder,

instead

set

memory

locations

A#@2

thru

A~P5

to

dump

the

data

stored

in

the

program

counter

storage

addresses

as

well.

Since

the

record

STATUS

light

is

lit

this

data

passing

back

and

forth

between

the

terminal

and

Gomputer

is

written

to

the

still

operating

recorder

but

is

however

ignored

when

loading

the

program.

Again

enter

a

P

for

punch.

The

DATA

light

will

again

come

on,

but

only

for

a

fraction

of

a

second

since

only

two

memory

locations

are

writ-

ten

to

the

tape.

Now

while

the

cassette

recorder

is

still

recording

flip

the

LOCAL/REMOTE

switch

to

the

LOCAL

position

and

type

in

on

the

terminal's

keyboard,

$9.

You

can

only

type

the

$9

if

you

have

the

16X

baud

rate

clock

fed

from

your

terminal

to

the

AC-30

Cassette

Interface

otherwise

omit

this

step.

Now

you

may

stop

the

recorder.

Don't

forget

to

flip

the

LOCAL/REMOTE

swtich

back

to

the

normal

REMOTE

position

and

reset

the

record STATUS

light

OFF.

Before

trying

to

load

this

same

program

you

might

want

to

momentarily

turn

the

computer

off

just

to

make

sure

the

memory

resident

program

is

destroyed

be-

fore

loading.

Reapplying

power

will

force

an

auto-reset

and

bring

up

the

resi-

dent

MIKBUG

8

firmware

on

the

SWIPC

6800.

Rewind

the

tape

to

the

beginning.

Make

sure

the

cassette

recorder's

volume

is

set

to

a

reliable

setting

and

depress

the

play

button.

Then

type

in

a

L

for

load

on

the

terminal's

keyboard

set

the

read

STATUS

light

ON.

The

DATA

light

will

remain

off

until

program

data

is

de-

tected

on

the

tape

at

which

time

it

will

begin

to

flicker.

When

it

stops

flick-

ering

it

means

that

the

program

data

has

been

loaded

to

the

computer's

memory

but

don't

forget

that

the

program

counter

data

was

also

written

to

the

tape

so

the

is

that

of

the

program

counter

being

loaded.

If

an

S9

was

written

to

tape

which

is

an

end

of

tape

marker,

a

*

will

be

printed

on

the

screen

upon

termination

of

loading.

The

read

STATUS

light

must

be

immediately

man-

ually

reset

OUT.

If

an

S9

was

not

written

to

tape,

a *

will

not

be

printed

and

the

read

STATUS

light

will

have

to

be

manually

reset

OFF

immediately

upon

load-

ing

the

second

string

of

data.

The

S9

is

then

manually

typed

in

from

the

ter-

minal's

keyboard

and

the

computer

responds

with

a

*,

The

program,

as

well

as

the

program

counter,

have

now

been

loaded.

Simply

typing

in

the

character

G

for

go

should

initiate

the

program.

S

186

Interfacing

to

a

SWIPC

6800

and

non-300

Baud

Terminal

System

Since

the

AC-30

Audio

Cassette

Interface

must

be

operated

RS-232

serial

at

300

baud,

it

cannot

be

implemented

serially

between

the

computer's

control

interface

and

the

terminal

system

on

non-300

baud

or

non-RS-232

terminal

systems.

The

only

option

the

user

has

in

these

cases

is

to

operate

the

AC-30

Cassette

Interface

thru

an

optional

serial

type

interface connected

to

one

of

the

unused

I/O

slots

on

the

computer

system.

The

big

disadvantage

here

is

that

the

MIKBUG

R

resident

tape

load

and

dump

routines

are

only

functional

on

the

I/O

slot

#1,

the

MP-C

Control

Interface

position.

Locating

the

AC-30

Cassette

interface

at

any

other

I/O

position

means

that

all

tape

load

and

dump

routines

will

have

to

be

keyed

in

manually

by

the

user

before

the

AC-30

Audio

Cassette

Interface

can

actually

be

used

to

load

programs.

The

other

problem

is

that

we

no

longer

have

any

way

of

deriving

motor

control

for

the

cassette

unit

since

motor

control

com-

mands

sent

out

thru

the

MP-C

Control

Interface

on

1/0

card

slot

#1

are

of

no

use

to

us.

On

top

of

that

the

standard

MP-S

serial

interface

option

does

not

have

enough

control

lines

available

to

provide

READER

ON,

READER

OFF,

RECORD

ON

and

RECORD

OFF

logic

control

for

the

attached

AC-30

Cassette

Interface.

For

these

reasons

it is

our

recommendation

that

the

AC-30

be

interfaced

to

the

computer

system

thru

a

separate

MP-C

Control

Interface

configured

for 300

baud

located

at

some

unused

1/0

card

position

on

the

interface

buss.

This

means

there

will

be

a

larger

overhead

in

software

for the

user

but

the

extra

unused

parallel

lines

on

the

parallel

PIA

integrated

circuit

may

be

used

for

AC-30

READER

ON,

READER

OFF,

RECORD

ON,

and

RECORD

OFF

control

functions.

Our

cassette

version

of

the

Editor/Assembler

software

already

has

I/O

routines

contained

within

to

drive

an

MP-C

Control

Interface

located

at

any

1/0

card

position

on

the

SWIPC

6800

Computer

System.

READER

ON,

READER

OFF,

RECORD

ON

and

RECORD

OFF

control

commands

may

be

taken

off

unused

pins

on

the

PIA

parallel

interface

chip.

The

lines

have

been

as-

signed

on

the

control

interface

when

using

the

Editor/Assembler

software

pack-

age.

It

is

suggested

that

you

use

the

same

assignments

to

maintain

consistency.

To

actually

use

these

logic/control

lines

within

your

own

programming

you

will

have

to

write

routines

within

your

own

cassette

I/O

software

package

to

put

a

TTL

compatible

1

to

1000

microsecond

negative

going

strobe

pulse

on

the

res-

pective

PIA

to

generate

the

desired

command.

A

connector

is

attached

from

these

MP-C

PIA

pins

to

the

control

lines

on

the

AC-30

Cassette

Interface

and

is

installed

as

follows.

Make

the

connections

from

the

indicated

pins

of

ICl

on

the

MP-C

Control

Interface

board

to

the

specified

pins

of

a

twelve

male

connector

shell.

Be

sure

to

make

the

wires

long

enough

to

reach

your

AC~30

Cassette

Interface

where

the

connector

will

be

plugged:

FROM

TO

MP-C

ICl

7

12

male

shell

female

#1]

RFAP

ow

MP-C

ICl

4

12

male

shell

female

#2

récom?

or

MP-C

ICl

6

12

male

shell

female

#3

SF4°

O*F

MP-C

ICl

5

12

male

shell

female

#4

7#<e*”

Terminal's

16X

clock

OUT

12

pin.male

shell

female

#5

Terminal's

16X

clock

IN

12

male

shell

female

#6

MP-C

ground

12

male

shell

female

#12

The

mating

connector

on

the

AC-30

Cassette

Interface

should

be

installed

just

as

is

shown

in

the

interconnection

drawing

for

the

SWTPC

6800

and

CT-1024

Terminal

System.

Other

connections

are

made

as

shown

in

the

appropiate

block

diagram.

All

~

19

-

data

connections

made

to

the

AC-30

should

be

thru

the

connector

provided

for

the‘

computer.

Since

there

will

be

no

terminal

connected

directly

to

the

AC-30

there

is

of

course

no

LOCAL

mode

of

operation

for

the

cassette

system.

You

will

have

to

write

your

own

cassette

tape

I/O

routines

in

order

to

be

able

to

load

and

dump

porgrams

to

and

from

the

AC-30

Cassette

Interface

which

is

now

interfaced

to

an

MP-C

Control

Interface

somewhere

other

than

I/O

Card

posi-

tion

#1.

You

should

be

able

to

use

the

MIKBUG

®

source

listings

of

the

tape

load

and

punch

routines

to

aid

you

in

writing

your

own

for the

cassette

interface.

If

the

routines

are

kept

short

enough

you

might

be

able

to

load

them

into

unused

areas

of

the

MIKBUG

8

RAM

which would

give

your

programs

complete

use

of

0-32K

user

memory.

The

tape

load

and

dump

programs

will

however

have

to

be

typed

in

manually

from

the

terminal

before

using

them.

How

It

Works

For

simplicity

the

cassette

interface's

circuitry

has

been

broken

up

into

three

separate

systems:

The

modulator/demodulator

circuitry,

the

switching

circuitry

and

the

power

supply.

1200

>h

The

modulator

works

by

feeding

a

4800

Hz

(16

X

300

baud)

clock

into

oe

Sh

Sg

divide

by

two

IC5B.

This

insures

a

50%

duty

cycle

required

by

the

modulator.2<,,

The

CARRIER

ENABLE

input

provides

a

means

of

supressing

audio

output

from

the

modulator.

IC5A

functions

as

a

divide

by

two

if

the

DATA

IN

line

is

high

and

/200.,

a

divide

by

one

if

the

DATA

IN

line

is

low*?s;This

gives

a

1200

Hz

tone

for

a

low

and

a

2400

Hz

tone

for

a

high.

This

resulting

output

is

then

fed

into

two

pole

active

filter

IC4A

where

it

is

converted

to

more

of

a

sinusoidal

audio

waveform

which

is

more

easily

handled

by

audio

recorders.

Incoming

audio

data

is

first

fed

into

a

high

pass

filter

consisting

of

RK

I

and

C5

and

then

onto

comparator

IC4B.

The

comparator's

0.5

volt

hysteresis

reduces

the

possibility

of

false

triggering.

The

+7.5

volt

zener

regulated

power

busses

feeding

IC4

are

necessary

to

stablize

this

hysteresis

value.

Zener

diode

clamp

D3

limits

comparator

IC4B's

output

to

CMOS

compatible

voltage

levels.

Each

time

the

comparator

changes

states

IC3C

and

IC3D

generate

a

5

microsecond

negative

pulse

at

IC3

1l.

This

pulse

is

repetative

when

data

is

being

received

and

pulls

capacitor

C7

down

to

ground

thru

diode

D4.

Capaci-

tor

C7's

output

is

in

turn

inverted

and

buffered

thru

IC3A

to

form

the

CARRIER

DETECT

output

signal.

This

same

negative

going

pulse

is

inverted

by

Ic2¢-where

it

feeds

four

seperate

circuits.

The

first

is

a

missing

pulse

detector

composed

of

transistor

Q2.

and

inverter

IC2B.

This

forces

the

buffered

CARRIER

DETECT

signal

low

whenever

several

cycles

of

audio

carrier

are

missed.

The

second

cir-

cuit

is

also

an

adjustable

missing

pulse

detector

but

this

one

times

out

whenever

-

1200

Hz

or

space

data

is

being

fed

into

the

demodulator.

Trimmer

resistor

R16

sets

the

period

for

this

timer.

The

third

circuit

driven

by

this

pulse

is

flip

flop

IC1A

which

outputs

the

demodulated

data.

This

DATA

OUT

line

is

high

when

1200

Hz

audio

is

being

demodulated

and

low

when

2400

Hz

audio

is

being

demodulat-

ed.

The

fourth

circuit

fed

by

the

pulse

is

IC2D

which

with

the

addition

of

the

output

of

IC3B

synthesizes

the

16

X

CLOCK

OUT

data.

Take

note

that

although

this

16

X

clock

is

accurate,

it,

by

design,

jitters.

Within

the

switching

portion

of

the

circuit,

integrated

circuit

halves

IC8A

and

IC8B

form

RS

status

latches

for

the

record

and

read

circuitry.

Either

latch

may

be

independently

set

or

reset

thru

manual

toggle

switches

on

the

in-

terface's

front

panel

or

thru

control

pulses

buffered

and

selectively

inverted

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5

3

&

o

8%

ae

Yo

St

°

?

vu

6

ecsten

Oa

eS7y

©

sd

©

lyuyoo_+-o

g

079

OlyYuoO

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:

e6ruo

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£10

bes

clad

&

osryuo

GROUND

to

compurer's

16x

cock

oureur

ORS/esn

T~

TO

COMPUTER'S

16X

CLOCK

INPUT

Cf

fess

bt

Te

to

computer's

rs-232

ineur,

42

Yeas

by

J

TO

COMPUTER'S

RS-232

OUTPUT

3

l

Ure

HT

ra

Y/RE

©

(2)

GROUND

=—4

ond,

LL.

BR

Vj

wet

LOCAL/REMOTE.

STOP

RECORD

——=

ORGS

LED

+5

STOP

READ

o——=

CRIP

REO

CONTROL

INVERT

ti?

TEP

START

READ

=m

i358

m/f

fee

2

start

econ

—==

{SL

VUsLE

TO

TERMIVAL'S

16X

CLOCK

OUTPUT

TO

TERMINAL'S

16X

CLOCK

(UART)

INPUT

CARRIER

DETECT.

CARRTER

DELAY

ENABLE

GROUND

TO

TERMINAL'S

RS~232

OUTPUT

To

TERMINAL'S

232

INPUT

SWTPC AC-30 User manual

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