NorthStar Z80 User manual

.J
I
NorthSIarCompuk2rslnc.
1440 Fourth Street
Berkeley, Ca. 94710
'North Star
zao Processor Board ZPB-A
Copyright @1977. North Star Computem. Inc,
1
.....
'25006
ZPB-DOC
Revision 3

North Star
Z80A PROCESSOR BOARD ZPB-A
Contents
Cautions . . . . . . . . . . . . . .
Introduction • . . . • . . • . . . •
Limited Warranty •. •••.••
Out of Warranty Repair .
ZBP-A
Parts List • • .• .•••
PROM Option Parts List . .• • •
Assembly Information ••
Figure lA: Component Identification
ZPB Assembly • • .• • • • • • •
ZBP Board Checkout • .••.•.
PROM Option Assembly and Checkout
Configuration Options •.•.•••
Theory of Operation ••••••
Appendix 1: Pulse Signal Detection •
Appendix 2: S-100 Bus Signals •••
Assembly Figures .....••••••
Schematic Drawings •.•• ~~ ••••
2
3
4
4
5
6
7
10
·11
•15
• 20
•21
• 24
•28
•29
• 30
•31
Copyright 1971, North Star Computers, Inc.
,
HEVISION 3
; pe '. p,

CAUTIONS
1. Correct this document from the errata sheets, if any, before
doing anything else.
2. Building this product from a kit is a complex, demanding
project. It should not be attempted without prior kit
build~ng experience.
3. Do NOT insert or remove the ZPB from the computer while the
power is turned on. Note that the power is not completely off
until the capacitors have discharged, several seconds after
turning of the power switch.
4. Do NOT insert or remove IC's from the board while the power is
turned on.
5. Be sure each 5 volt regulator is generating 5 volt output
voltage before installing any IC's.
6. Be careful to insert all IC's in correct positions and with
correct orientation. Be sure all IC pins are correctly
inserted into the socket holes and are not bent under the IC
and
are not outside the socket.
7. Carefully observe the anti-static handling procedure for the
static sensitive devices (these are the Z80A and the 2708 PROM
in the PROM option). The procedure is described in the
Assembly Information section of this manual.
North Star Z80A PROCESSOR BOARD
2

-INTRODUCTION
The North Star Computers Z80A Processor Board (ZPB) provides Z80
microprocessor capability on the S-100 bus. The use of the Z80A
chip allows full speed 4MHz operation as a standard feature. The
ZPB can be used in any standard S-100 bus computer and will
operate in conjunction with nearly all other S-100 bus boards.
However, the ZPB has been specifically designed to integrate into
the North Star Computers HORIZON computer system. In addition to
the Z8'0A microprocessor and support logic - to interface .. to the ...
standard S-100 bus, the ZPB contains the following features and
options:
-1. AUTO-JUMP feature that will cause an automatic jump to any
address at power-on or reset.
-2. VECTORED INTERRUPTS. ZPB logic will respond to eight levels
of interrupt requests, determine the highest priority request
pending and generate the appropriate RST instruction. The
logic may be disabled to allow the function to be performed on
another board.
3. FRONT PANEL INTERFACE for direct connection to IMSAI and other
similar front panels.
4. ADDRESS MIRROR feature to simulate the input/output
characteristics of the 8080 microprocessor. This feature
maintains compatibility with some S-100 bus peripheral boards.
Address mirroring may be disabled to allow use of the more
powerful Z80 protocol.
-S. PROM OPTION. lK of 2708 type erasable PROM can be added to
the ZPB. This allows coniiguration of systems that require
resident monitor and bootstrap programs.
If you have purchased the ZPB as a kit, first skim this entire
manual. Before beginning assembly, carefully read the Assembly
Information section.
Whether you purchased the ZPB as a kit or assembled, read the
Configuration section before attempting to use the ZPB. Note
that a Z80 Technical Manual has been included to fully describe
the operation of the Z80A.
3
North Star Z80A PROCESSOR BOARD
. ; ::.'.: .; ';: Vi
"";jM" .,JJfir.Je5fEf. n, .. ; ' M •••••••• ~.·.-_ ••• -.·._.· • .:.·.-.· ••• ".~o-._ ..

LIMITED WARRANTY
North Star Computers, Inc. warrants the electrical and mechanical
parts and workmanship of this product to be free of defects for a
period of 90 days from date of purchase. If such defects occur,
North Star Computers, Inc. will repair the defect at no cost to
the purchaser. This warranty does not extend to defects
resulting from improper use or ~ssembly by purchaser, nor does it
cover transportation to the factory. Also, the warranty is
invalid if all instructions included in the accompanying
documentaticm' are not carefully followed. Should 'a unit returned
for warranty repair be deemed by North Star Computers, Inc. to be
defective due to purchaser's action, then.a repair chargE~ not to
exceed $30 without purchaser's consent will be assessed. ANY
UNIT OR PART RETURNED FOR WARRANTY REPAIR MUST BE ACCOMPANIED BY
A COpy OF THE ORIGINAL SALES RECEIPT. This warranty applies to
units located outside the United States of America only if all
costs and arrangements for transportation of the product to and
from the factory are borne entirely by the customer. This
warranty is made in lieu of all other warranties, expressed or
implied, and is limited to the repair or replacement of the
product. No warranty, expressed or implied, is extended
concerning the completeness, correctness, or suitability of the
North Star equipment for any particular application. There are
no warranties which extend beyond those expressly stated herein.
OUT OF WARRANTY REPAIR
If your unit is out of warranty and you are unsuccessful at
diagnosing or repairing the problem, o~t-of-warranty service may
be arranged with a local dealer or other experienc~d local
computer technician. Alternatively, any North Star products may
be shipped PREPAID to the North Star address with a clear written
description of the problem. Include as many details as possible
about the problem and about your system configuration. Your unit
will be returned, C.O.D., within 30 days after receipt by North
Star. Out-of-warranty repair service is billed at the rate of
$25.00 per hour. If you wish to place an upper limit on the
amount of time spent on your unit, mention this in the written
description.
;: ,so.
North Star Z80A PROCESSOR BOARD
4
1

-ZPB-A
PARTS
LIST
1- ZPB Manual
t
Z80
Technical Manual
1
ZPB printed circuit board,
5"
x 10"
~
1 40-pin IC
socket
7
20-pin
IC
sockets
14 16-pin IC
sockets
14 14-pin
IC sockets
1 16-pin DIP header
1 04
IN4l48 diode
2
~
volt regulators, 7805 or
340T-5
2 heat
sinks,
6H'l7B-14
1 crystal, 8f.tHz
2
6-32x3/8"
machine screws
2#6
lock washers
?
6-32 nuts
-
Integrated
Circuits
-3-
74LS00
1 74LS132
2
74LS02
1 74LS148
1
74LS03
.,
74LS175
oJ
2 74LS04
7
74LS241
1
74LS08
2 74LS257
74LS14
1 7404
74LS32
.,
74367
-1
74LS74
1 8T97
74LS75
1Z80A
-
Resistors
1 100 ohm (brown-b1ack-brown)
1 330 ohm (orange~orange-brown)
2 470 ohm (yellow~violet-brown)
11 lK ohm (brown-black-red)
110K ohm (brown-black-orange)
4 lK ohm networks, Part No. 10-9-l-RIK
1 2.2K ohm network, Part No. 10-9-1-R2.2K
-Capacitors
33pf
470pf
.047uf
6.8uf
39uf
100uf
-dipped mica (may be marked "330J03")
dipped mica
ceramic disc
dipped tantalum
dipped tantalum
electrolytic
-NorthStar Z80A PROCESSOR BOARD

-PROM OPTION PARTS LIST
-74LS136 IC
2708 EPROM
+12 volt regulator, 78L12
-5 volt regulator, 79L05
24-pin-rC socket
14-pin IC sockets
14-pin DIP header
1K resistor (brown-black-red)
3.9K resistor (orange-white-red)
3.9K resistor network, Part No. 10-9-1-R3.9K
2.2uf dipped tantalum capacitors·
-North Star Z80A PROCESSOR BOARD

ASSEMBLY INFORMATION
-Read completely through each section before beginning the first
instruction step of that section. Perform all operations in the
sequence indicated. Read each step entirely, including any notes
that accompany the step, before beginning to follow the step.
-WORK AREA AND TOOLS
-Start with a clean, well-lit and well-ventilated area to work.
The area should be large enough to accommodate the kit, t~ols,
parts and assembly instructions. Suggested tools are:
screwdrivers, needle-nose pliers, diagonal cutters, soldering
iron, solder, and masking tape. Anumber of tests will require
usin,5J a VOM (ohmmeter-voltmeter), or VTVM. Also highly
desirable, but not necessary, a~e an IC inserter;a~~rew-holding
screwdriver, an oscilloscope or logic probe, and an l~xtender
card. [Note that if you do not have an oscilloscope or logic
probe, waveforms can be detected by one of the procedures
described in Appendix 1.]
SOLDERING TIPS
-For best results use a15 to 25 watt soldering iron or an iron
with a temperature controlled tip (approximately 700 degrees).
The tip should be no widet than the solder pads on the printed
circuit board. Use only a fine gauge rosin core solder (60/40 or
63/37). Do NOT use acid core solder as this can severely damage
a
printed circuit board. When soldering, keep the soldering iron
tip on the pad just long enough for the solder to completely
flow. If the solder does not draw up the wire then more solder
is required. Do not use so much solder that it overflows the
pad. If a solidified joint is not shiny, it may be a cold solder
joint and should be remelted. The soldering iron tip should be
cleaned frequently by wiping on a damp sponge
-When you have completed assembly of a board, inspect it for
unintended solder connections or "bridges", as well a~ unsoldered
leads. After soldering, it is recommended that the rosin flux be
removed from the board usirig flux remover, FREON or paint-thinner
type solvent. This will make looking for soldering problems
easier and give the board a clean, professional appearance.
IC SOCKET INSTALLATION
-Integrated circuit (IC) sockets can be installed by first
inserting them into the printed circuit board, then placing
another flat board over the IC sockets arid finally turning over
this sandwich. Be sure that each IC socket is inserted into the
proper location and is oriented such that pin 1 of the socket
corresponds to the pin 1 indication on the PC board layout
legend. (Refer to figure lA to identify pin 1on an IC socket.)
To solder IC sockets, first solder just two opposite corner pins
North Star Z80A PROCESSOR BOARD

PRINTED CIRCUIT BOARD LAYOUT
-DIP HEADER SOLDERING
-RESISTOR AND CAPACITOR INSTALLATION
8
North Star Z80A PROCESSOR BOARD
To install resistors or capacitors, first make right angle bends
in the leads to fit the PC board hole spacing. (Some capacitor
leads are already appropriately spaced and do not need bending.)
Then insert the leads as far as possible through the correct
holes in the PC board and spread the leads slightly on the solder
side of the board to keep the part in place. After a group of
resistors or capacitors has been inserted, then solder the leads
on the solder side of the board and snip off the excess leads as
close to the board as possible. Use caution to avoid eye injury
from flying bits of wire. Save the lead clippings "for later use
in making jumper connections.
Pin numbering conventions for the S-100 edge pins are as follows:
When viewing the component side of the board (with the pin edge
facing down), pins 1,2, ••• ,50 range from left to right. When
viewing the solder side of the board, pins 100, 99, .•• , 51 range
from left to right.
The white component layout legend is printed on the component
side of a printed circuit (PC) board. All components are
inserted f~om this side (component side) and soldered on the
other side (solder side). Locations on the PC board are
identified by two-character codes as marked on the board: a digit
followed by ~ letter indicating the horizontal and vertical
coordinates of the location. Note that in North Star kits, IC's
can be found on styrene pads in positions corresponding to their
intended locations on the PC board.
When making jumper connections on aDIP header, solder resistor
or capacitor lead snippings ~etween the leads to be connected.
When more than two pins are to be connected together, bend a
single wire so that it routes to each pin, and solder each pin
once. Inse~t the header in an IC socket on a PC board to hold it
during soldering. Overheating the pins with the soldering iron
will melt the plastic of the header. If there are multiple
jumpers on a header, make sure that no unintended connections are
made by carefully routing the jumpers, or by insulating each
jumper with some wire insulation.
-for all sockets being installed. Then remelt the corner
connections while applying pressure down on the board. This will
remove any gaps that may be present ~etween the IC sockets and
the PC board. Finally, solder the remaining pins of the IC
sockets. -

-MOS INTEGRATED CIRCUIT HANDLING
-Some North Star PC boards use some MOS-type Ie·s. These parts
are identified as such in the instructions. MOS devices can be
damaged by static electricity discharge, so special handling is
necessary to protect them. Handle MOS devices as little as
possible and avoid touching the pins. Place the conductive foam
or tube which contains the MOS device onto the PC board before
removing the device from the foam or tube. Also, be sure both
hands are touching the foam or tube when the device is removed
from
the foam or tube.
-Once a MOS device has been installed in a PC board, handle the
board as little as possible. Of course, never insert or remove
any IC while power is applied to the board, and never remove or
insert a PC board while power is applied to the motherboard.
4
-,
9
-North Star Z80A PROCESSOR BOARD

positive (+) lead
Axial Lead
Electrolytic Capacitor
c::. ===~OJ)E)=======
-Resistor
Transistor and
Regulator (To-92)
"positive
(+) lead
Quick-Connect
Lug Ceramic
Disc
Capacitor
Dipped
Mylar
Capacitor
Dipped
Mica
Capacitor
Dipped
Tantalum
Capacitor
Integrated Circuit (lC) IC
Socket
DIP Header
Figure 1A. Identification and orientation of components.

ZPB ASSEMBLY
-Before beginning assembly of the ZPB, first check that you have
all the parts listed in the parts list.
-Note that in-the following instructions, "left" and "right" refer
to those directions when viewing the component side of the PC
board with the 100-pin edge facing down.
-Using-an ohmmeter, check for open circuits between the pair
of solder pads for each of the following seven capacitor
locations: C22, C23, C25, C26, C27, C28, and C29. If any
shorts are found, locate and correct the problem or return
the PC board for replacement.
-Insert and solder the 40-pin IC socket at location 3C,
following the procedure given in the Assembly Infor~ation
section.
-Insert and solder the seven 20-pin IC sockets with correct
orientation.
-Z4. -Insert and solder a 16-pin IC socket at location IG. Note
that this socket has reverse orientation from all the
others, with pin 1 in the upper right corner.
zs. -Insert and solder the remaining thirteen 16-pin sockets with
correct orientation.
Z6. -Insert and solder the fourteen 14-pin sockets with correct
orientation. Do not install sockets in locations 5C, 5D,
and 5E (inside dashed line) unless you are assembling the
PROM option at this time.
-~ -Insert and solder the five single-in-line (SIP) resistor
~ networks labeled RNl, RN2, RN4, RN5, and RN6 on the layout
legend. RN6 is a2.2K oh~~networkand the remaining four
are lK ohm networks. RN3 is part of the PROM option.
Orient each SIP so the end marked with a "I" (sometimes this
end has a beveled corner) corresponds to the end marked with
a dot on the layout legend.
-Insert and solder the following sixteen resistors. Refer to
the Assembly Information section for resistor installation
procedures.
-Resistor V~lue
-Color-code
Location
-470 ohm
-yellow-violet-brown IF
11
North Star Z80A PROCESSOR BOARe

12
-IF
2E
5G
4F
4C
6B
6B
4G
7C
7A
7A
8F
8G
8G
BG
yellow-violet-brown
brown-black-red
brown-black-red
brown-black-red
orange-orange-brown
brown-black-red
brown-black-red
brown-black-red
brown-black-red
br<Dwn-black-red
brown-black-red
brown-black-red
brown-black-orange
brown-black-brown
brown-black-red
ohm
ohm
ohm
ohm
ohm
ohm
ohm
ohm
ohm
ohm
ohm
ohm
ohm
ohm
ohm
470
lK
lK
lK
330
lK
lK
lK
lK
lK
lK
lK
10K
100
lK
North Star Z80A PROCESSOR BOARD
solder the IN4148 diode at location 8G. The end
de marked with a band is theca thode end and
oriented toward the top of the board.
d solder the 8MHz crystal at location IF. Make
Ie bends in the two leads so the crystal will lie
parallel with the PC board. To hold the crystal package in
place, use a piece of snipped resistor lead to solder the
top of t e crystal package to the corresponding hole in the
board. ~ little space should be left between the crystal
and the PC board to avoi~ the possibility of shorts.
Insert and solder the l00uf electrolytic capacitor (C29)
located ear 8A. The positive end (marked with a "+" or a
red dot) should be oriented toward the right as indicated on
the layo t legend. Some capacitors mark the negative end
with a " " instead of the p6sitive end.
Insert a1d solder the 39uf tantalum capacitor (C2l) near
location 7G. Be sure to orient the capacitor so that the
lead mar ed with a"+" is inserted through the hole marked
wi th a II, ".
Z12. - Insert atd solder the two 6. 8uf tantalum capacitors (C22 and
C23) at ocations 8F and 8G. Be sure to orient the
capac ito s so that the lead marked with a"+" is inserted
through he hole marked with a "+".
Insert atd solder the 470pf dipped mica capac i tor (Cl) -at
location IF. Some 470pf capacitors are marked 1147lJO".
Insert atd solder the 33pf dipped mica capacitor (C5) at
location 2F. Some 33pf capacitors are marked "330J03".
Insert a~d sOlder, the nineteen ceramic disc bypass
capac ito s in locations marked with an asterisk on the
layout 1 gend. "t ~
Z14.
ZI6.
Z10.
,)
R2
J () "R3
( r'-RS'
( ) ,-R6
( ) "-R7 .,'
()<Rgj
( )( R9-
~-"~i "
,~' () R
,L--- ( ) 'R~")
( )Rl-'
( 'fBI j
( l::-gJ
( )'-Hl_ 0
( ) ,,' Rl 7)
'{ () ,:Ri8)
L:""'~
~v' Insert
of the
should

-NOTE: The 8MHz crystal is used for 4MHz operation of the
processor. If 2MHz operation is desired, then a 4MHz
crystal (not supplied) should be used. See the
Configuration section for details.
-ZI7. Recheck the circuits between the capacitor leads as in step
Zl and make sure they are still open circuits. Note that
the capacitors which have been installed may cause the
ohmmeter needle to jump when first contact is made but the
indication should rapidly return to a high resistance.
-ZI8. Insert and solder the two 5-volt regulators (Q3 and Q4).
These parts will be marked "7805" or."340T-5". Bend down
the three leads of the regulator 90 degrees so that the
leads go into the correct holes while the machine screw
holes line up. Install the heat sink and regulator so that
the following sequence results from bottom to top: 6-32
machine screw head, PC board, heat sink, regulator, lock
washer, and nut. Finally, make sure the leads do not touch
each other or the heat sinks and then tighten the machine
screw and solder the regulator leads.
-NOTE: Heat sink grease may be used though it is not
generally needed. Tightening the bolts too tight can crack
the PC board.
-With the computer power off, plug the partially assembled
board into the motherboard. Then turn on the power. with a
DC volt meter check that both regulators are generating 5
volts output. These voltages can be measured across the
pins of C22 and C23. Wait afew minutes and measure again.
The regulators should not get very hot in this
configuration. However, with all parts installed it is
normal for the regulator to feel quite hot to the touch.
Remember to turn off the power before removing the board.
-Z20. Construct a 16-pin DIP header with jumpers set up for a
starting address of E800 hex. This is the standard HORIZON
starting address. If some other~tarting address is
desired, change the header after G9mpleting the checkout
instructions. See figure IZ for the details of the header
configuration. Refer to the Assembly Information section
for header construction procedures. Plug the completed
header into location 2E (the POJ ADDRESS socket) with the
correct orientation.
-Insert the 33 integrated circuits (all except the Z80A
chip). Be sure that all IC's have pin I oriented to the
bottom left corner. Do not insert any IC's inside the area
for the PROM option (outlined with a dashed line).
-Recheck the regulator output voltages as in step Z19.
13
-North Star Z80A PROCESSOR BOARD

Inspect the board in a good light to insure that:
C. all parts are installed in the correct l~cations with the
correct orientation.
-Remove the PC board from the computer and then plug in the
Z80A chip with correct orientation. Refer to the Assembly
Information section for MOS device handling procedures.
14
A. all solder joints are good, i.e. there are no bridges of
solder beween adjacent solder joints, no unsoldered
joints, and no cold solder jo~nts indicated by a dull
finish on the solder.
B. all-IC pins are in the IC socket holes, nbt outside the
socket and not folded under the chip. Pins folded under
can often be detected by sighting down arow of chips to
see if there is any blockage of light under the chips.
-North Star Z80A PROCESSOR BOARD
The ZPB is now completely assembled. Proceed to the ZPB Board
Checkout section.

BOARD CHECKOUT
- I
The following checkout ·Iprocedure should be followed for a newly
assembled board. It can also be used to diagnose problems in
previously operational boards.
- This checkout procedure
l
assumes that no other board besides the
ZPB is plugged into the S-100 bus. This makes it possible to get
the ZPB operational eveh if no other board in the system is yet
working. This procedure assumes only that the correct
unregulated voltages have been applied to the bus,that the
computer has a reset switch, and that the bus lines are not
shorted to each other. I,
The following terms arelused in specifying expected test results.
1
GND
LOW
HIGH
+5V
AC
ground, 0 volts DC
logic zero, 0-.7 volts, normally about .3 volts
logic on~, 2.4-5.0 volts, normally about 3 volts
+5 voltslfrom power supply
Signal w~th pulses (as opposed to DC signal)
15
When referring to the n~me of a signal from the schematic
drawings, if the signal lis identified with a bar over its name
then the name of the signal is followed by a slash (E!.g., STORE/)
in the checkout instructions. When describing an AC pulse, the
notation (±W,P) refers tio a positive or negative pulse with a
width of Wand a per iod lof P. For example, a posi tiv'e pulse of
width 125 nanoseconds a~pearing every 25 microseconds would be
represented as (+125n~,25us). See Appendix 1 for details on how
to detect pUlse signals.1
-The abbreviation MB befol1re a pin number indicates a bus pin on
the motherboard. ,
I'
If an oscilloscope will ~e used to test tHe board, a "scope
ground" may be installedl by soldering a "bridge" of jumper wire
between the two PC board
l
holes that connect edge connector pins
50 and 100 near location 2A. Note that either of the two
regulator machine screwslcan also be used for ground test points.
Cl. Check for correct clock signals on the ZPB as follows:
,
A. Install a jumper wire at PE (near location 4G) if the PE
trace was has been cut.
B. Remove the lW jumpei (near location 6G) if it was previously
installed. I
North Sttar Z80A PROCESSOR BOARD

I
-C. -Install a jumper wire at MW (near location 6A) - i.f the MW
trace has been cut.
D. with the computer power off, install" only the ZPB in the
computer motherboard.
E. -Turn on the computer power and chec~ for the following
signals. Note that all timing signals given below assume
the ZPB is configured for standard 4MHz o~eration.
-
Signal
-
Location
-
Description
-PHI -
Z80 pin 6--
AC,
(+125ns,250ns)
PHI 2
MB pin
24 AC, (+125ns , 250ns )
PHI 1
MB pin
25 AC, (+62ns , 25 011s )
2MHZ
CLOCK/ MB pin
49
AC, (-25"0ns,500ns)
-If any of these are wrong, -trace back to the crystal -to
determine the cause.
-C2. -This step will check the reset logic. Use the same setup as
the previous step and check the following signals while
alternately depressing and releasing the computer reset
switch.
-
Switch
Switch
-
Signal
-
Location
Released
Depressed
-RESET/
MB pin
75
--
LOW HIGH
7G
pin
6 HIGH
LOW
-RST/
5G
pin
6 "
LOW
HIGH
POC/
MB
pin
99
LOW HIGH
-C3. -Check
the auto-jump logic follows: as
A. -Leave the board configured as in the previous StE~p.
-B. -Turn off the computer power and remove the ZPB from the
computer. Temporarily connect the PRDY signal to ground by
soldering a piece of jumper wire beween 7F pin 5 and 7F pin
7 on the solder side of the ZPB.
-C.
-Install only the ZPB in the computer motherboard and then
turn on the power and depress and release the reset switch.
The processor should pause im~ediately after performing the
auto-jump sequence and just before executing the first
instruction at the auto-jump address. Check that the SMI
signal at motherboard pin 44 is HIGH.
D. Assuming the jump address specified on the header at
location E2 is E800, theq E800 should be on the motherboard
address lines. HIGH signals should be observed on the
following motherboard pins:
-North Star Z80A PROCESSOR BOARD

-~
pins 32, 85, 86, and 87
-LOW signals should be observed on the following motherboard
pins:
\
s 29, 30, 31, 33, 34, 37, 79, 80, 81, 83, 84
11.
PRDY
should have execu a si 1 struct (JMP
gone into a wait state duri instruction
address. The Theory of ration sect n
s
the auto-jump sequence. If 5Ml shh but
is wrong, check the data paths r h POJ
multiplexors. If 5Ml is LOW, sk to next
see if the processor can execute tructions at
5Ml has an AC signal, check wa t1 ic from
WAI
C4.
-I
-~hi~ ste~ checks out the Z80A while executing a one
Ins~ructlon program.
A. With\ the power off, remove the jumper -from PRDY to ground
from the ZPB.
B.-Turn~on the power and then depress and release the reset
swit h. The Z80 should be executing an RST 7 instruction
repe tedly. Observe that all the data input (DI) lines are
HIGH by checking the following motherboard pins:
-p~ns 41, 42, 43, 91, 93, 94, and 95
C. If you have an oscilloscope, then check that the signals
ZD0-~D7 are HIGH during Ml at the Z80A chip pins:
-p~ns 14, 15, 12, 8, 7, 9, 10, and 13
D. C~eck\ that the following motherboard address lines are AC
slgna~s:
-pips 29-34, 37, and 79-87.
"
E. The RST 7 instruction causes a subrouilne call to location
0038 hex, thus the stack address stored will be 0039 hex
(stored as alternating 00 byte and 39 hex byte). Thus, if
you h ve an oscilloscope, observing the data output bus
(DO), the following motherboard bus pins should have AC
signa s that go low twice every 2.75 microseconds:
35, 40, 88, and 90.
17
-and
th\:
Signalr
pin~
following motherboard bus pins should have AC
that go low once every 2.75 microseconds:
36, 38, 39 -and 89
North Star Z80A PROCESSOR BOARD

F. Check for the following signals at the Z80 chip:
Signal
PHI
Ml/
INT/
NMI/
WAIT/
• 'RST/
Vcc
ground
Location
pin 6
pin 27
pin 16
T;>in 17
pin 24
pin 26
pin 11
pin 29
Description
AC, (+125ns,250ns)
AC, (-500ns,2750ns)
HIGH
HIGH
HIGH
HIGH
+5V
GND
G. The following signals should be observed on the mot:-herboard
bus lines:
Signal
XRDY
VI0/
VII/
VI2/
VI3/
VI4/
VI5/
VI6/
VI7/
NMI/
STAT-DSBL/
CC-DSBL/
ADDR-DSBL/
DO-DSBL/
PHLDA
PWAIT
PINTE
SMI
SOUT
SINP
SMEMR
SHLTA
SSW-DSBL/
PMREQ/
PRFSH/
MWRITE
RUN
PINT/
PHOLD/
PSYNC
PWR/
PDBIN
SwO/
Location
pin 3
pin 4
pin 5
pin 6
pin 7
pin 8
pin 9
pin 10
pin 11
pin 12
pin 18
pin 19
pin 22
pin 23
pin 26
pin 27
pin 28
pin 44
pin 45
pin 46
pin 47
pin 48
pin 53
pin 65
pin 66
pin 68
pin 71
pin 73
pin 74
pin 76
pin 77
pin 78
pin 97
Description
HIGH
HIGH
HIGH
HIGH
HIGH
HIGH
HIGH
HIGH
HIGH
HIGH
HIGH
HIGH
HIGH
HIGH
LOW
LOW
HIGH
AC, (+500ns,2750ns)
LOW
LOW
AC , (+375ns , 2750n s)
LOW
HIGH
AC, 4 -pulses every 2750ns
AC, (-475ns,2750ns)
AC, (+250ns twice,2750ns)
HIGH
HIGH
HIGH
AC, 3 +pulses every 2750ns
AC, (-250ns twice, 2750ns)
AC, (+360ns, 275011s)
AC, (-250ns twice, 2750ns)
North Star Z80A PROCESSOR BOARD
18

-If these checkout steps have been successful, then the ZPB has
successfully done an auto-jpmp and executed a simple program.
Therefore, most of the circuits on the ZPB have been tested. The
ZPB should now have its configuration options set. Be sure to
remove all special jumpers added during the checkout. It is then
ready to be used in conjunction with the other boards in the
computer system. If the PROM option is being used, install it at
this time.
\
If the board is still failing then the problem maybe a result
of any of the following less likely conditions: dirty edge
connector contacts, bad Rarts other than the IC's, bad
connection in an IC socket, or introduction of a short or open
in the traces on the board.
Diagnosis of a problem in a-previously operational board will
usually be successful using the following procedure:
- - I-
I. Determine that the ZPB is in fact the board that has the
problem by attempting to\use it in another computer.
-2. Check that the regulator-outputs are correct. Then, in an
ord~rly .fashion begin replacing IC's in the ZPB with known
good paE-ts until the problem disappears. If a board that was
working has not been subjected to any abnormal abuse then an
IC failure will be the cause of the problem in nearly every
case.
19
-North Star Z80A PROCESSOR BOARD