IBM 3278 Use and care manual

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IBM Personal Computer
3278/79 Emulation
Adapter Technical .
Reference
1502336

First Edition (October 1983)
Changes are periodically made to the information herein; these
changes will
be incorporated in new editions of this publication.
Products are
not stocked at the address below. Requests for
copies of this product and for technical information about the
system should be made to your authorized IBM Personal
Computer dealer.
A Reader's Comment Form is provided
at the back of this
publication.
If this form has been removed, address comments to
IBM Corporation, Personal Computer, P.O. Box 1328-C, Boca
Raton, Florida 33432. IBM may use
or distribute any of this
information you supply in any way it believes appropriate without
incurring any obligations whatever.
© Copyright International Business Machines Corporation 1983
ii

FEDERAL COMMUNICATIONS
COMMISSION RADIO FREQUENCY
INTERFEREN
CE STATEMENT
Warning: This equipment has been certified to
comply with the limits for a Class B computing
device, pursuant to Subpart J
of Part 15 of FCC
rules. Only peripherals (computer input/output
devices, terminals, printers, etc.) certified to comply
with the Class B limits may be attached to this
computer. Operation with non-certified peripherals
is
likely to result in interference to radio and TV
reception.
INSTRUCTIONS TO USER
This equipment generates and uses radio frequency
energy and if not installed and used properly, i.e., in
strict accordance with the operating instructions,
reference manuals, and the service manual, may cause
interference to radio
or television reception. It has been
tested and found to comply with the limits for a Class B
computing device pursuant to
Subpart J of Part 15 of
FCC Rules, which are designed to provide reasonable
protection against such interference when operated in a
residential installation.
iii

iv
If this equipment does cause interference to radio or
television reception, which can be determined by turning
the equipment off
and on, the user is encouraged to try
to correct the interference by one or more of the
following measures:
• Reorient the receiving antenna.
• Relocate the equipment with respect to the receiver.
• Move the equipment away from the receiver.
• Plug the equipment into a different outlet so that
equipment and receiver are on different branch
circuits.
• Ensure that side option mounting screws, attachment
connector screws, and ground wires are tightly
secured.
• If peripherals not offered by IBM are used with this
equipment, it
is suggested that you use shielded,
grounded cables with in-line filters, if necessary.
If necessary, consult your dealer service representative
for additional suggestions.
The manufacturer is not responsible for any radio or TV
interference caused by unauthorized modifications to this
equipment. It
is the responsibility of the user to correct
such interference.
CAUTION
This product is equipped with a UL-listed and
CSA-certified plug for the user's safety. It is to be
used in conjunction with a properly grounded
receptacle
to avoid electrical shock.

Preface
This publication provides technical information about the IBM
Personal Computer 3278/79 Emulation Adapter Card. This
manual describes the hardware design and provides interface
information for the IBM Personal Computer and IBM Personal
Computer XT.
The information in this publication
is for reference, and is
intended for hardware and software designers, programmers,
engineers, and interested persons who need
to understand the
design and operation of the IBM Personal Computer.
v

vi

Contents
Section 1. IBM Personal Computer 3278/79 Emulation
Adapter
........................................ 1-1
Introduction ................................. 1-1
Adapter Block Diagram
........................ 1-2
I/O Address Locations ......................... 1-3
Interrupt/Status Register (2DO) ................. 1-4
Visual/Sound Register
(2Dl) ................... 1-5
Cursor Address Register (2D2, 2D3)
............. 1-6
Control Register (2D4)
........................ 1-7
Scan Code Register (2D5)
...................... 1-9
Terminal ID Register (2D6)
................... 1-10
Memory Address Locations .................... 1-11
Accepted Commands
......................... 1-12
vii

viii

Section 1. IBM Personal Computer
3278/79 EmulationAdapter
Introduction
The IBM Personal Computer 3278/79 Emulation Adapter card
supports emulation
of the base 3270 data stream and controls
communication between the IBM Personal Computer and an IBM
control unit. All system control signals and voltage requirements
are provided through a 2
by 31 position card edge tab. A coaxial
connector (type
BNC) joins this adapter card to the control unit.
The adapter card will accept, decode, and execute commands
issued from the control unit
or the IBM Personal Computer. All
information from the control unit
is sent in the form of a 12-bit
frame over a coaxiallinlc Transition checks include mid-bit
transition and transmission parity.
1-1

Adapter BlockDiagram
Coax
line Interface
Personal
~
Transformer
~
Control
~
Control
Computer
~
Interface
~
,~
,If
Data Bus
~
),
~~
"
Buffer
'"
-
Buffer
~
Control
~
Adapter Block Diagram
1-2

I/O Address Locations
This table describes the 110 address locations for the registers
that define and control the emulation adapter.
Base Address Low Address
Hex I/O Space
Bits
Register
200 000
I nterru pt/Status Register
201 001 Visual/Sound Register
202
010
Cursor Address Register 7-0
203 o1 1 Cursor Address Register 15-8
204
100
Control Register
205 1 0 1 Scan Code Register
206 1 1 0 Terminal 10 Register
I/O Address Locations
1-3

Interrupt/Status Register (2DO)
This 8-bit register on the emulation adapter is accessed by the
IBM Personal Computer. Bits 0 through 5 are Interrupt (I) bits,
which are set
by the emulation adapter and reset by the IBM
Personal Computer. Bits 6 and 7 are Status (S) bits, which are set
and reset
by the adapter.
Note: Interrupt
Level-2 is used by the emulation adapter.
Bit I/S
Function
0 I
Keystro ke Accepted
1 I
Reset Command Decoded
2 I
Visual/Sound Register Updated
3 I
Reserved
4 I
Base Buffer Modified Complete
5 I
Load I/O Address Command Decoded
6 S
Buffer Being Modified
7 S Interrupt
Generated
Interrupt/Status Register
1-4

Visual/Sound Register (2Dl)
This 8-bit register is set and reset by the emulation adapter
except for the sound alarm (bit 6) which
is reset by any Write
operation from the IBM Personal Computer to this register
with any data.
No other bits are affected by a Write operation
I from the IBM Personal Computer to this address. Each time this
register
is loaded by the adapter logic, bit 2 in the Interrupt/Status
Register
is set.
Frame
Bit
Function Bit
0
0= 80 characters per line 3
1 Inhibit Feature Step of Address Counter 5
2
Inhibit Display 6
3 Inhibit Cursor
7
4
Reverse Cursor 8
5
Blink Cursor 9
6 Sound Alarm
7 Enable CI icker
Visual/Sound Register
1-5

Cursor Address Register (2D2, 2D3)
This 16-bit register is internal to and is set by the emulation
adapter. This register requires two addresses and can be read by
the
IBM Personal Computer. This register contains the current
value of the
I/O Address Counter. In 3278/79 emulation mode,
this register indicates the location of the cursor.
1-6

Control Register (2D4)
This is an 8-bit Read/Write register internal to the emulation
adapter and accessed by the IBM Personal Computer.
It requires
one address to read and write.
Bit
Function
0
Coax Enable
1
Reserved
2
Reserved
3
Keystroke Available
4
Reserved
5
Test
6
Reserved
7
Disable Interrupt
Control Register
1-7

Bit 0
This bit is set by the IBM Personal Computer,
causing the emulation
adapter to become enabled and
on-line. After this bit is set, the first POLL causes a
POR response to be sent to the control unit. The bit
is initially reset during hardware
power-on. It is also
reset
by the RESET command or by the IBM Personal
Computer.
When this bit is reset, the emulation
adapter ignores all transmissions from the control
unit. Thus, it causes the control unit
to timeout and
set the "GO TO SLEEP" latch for that line.
Bit 1 Reserved.
Bit 2 Reserved.
Bit 3 This bit is set
by the IBM Personal Computer and
notifies the emulation adapter that the Scan Code
Register has been loaded. This data is then handled as
a keystroke. This bit is reset by a
POLL ACK or
RESET command from the control unit.
Bit 4 Reserved.
Bit 5 This bit is set by the IBM Personal Computer. It
allows the IBM Personal Computer to do limited
functional testing of the IBM Personal Computer
3278/79 Emulation Adapter card. The coaxial link is
automatically disabled.
1-8

Bit 6 Reserved.
Bit 7 This bit is initially reset by the hardware power-on
cycle. Then it is set and reset by the IBM Personal
Computer. Setting this bit inhibits the sending
of
interrupts to the IBM Personal Computer, but it does
not prevent setting the interrupt/status bit (0-5). If
an interrupt is set when the Mask bit is on, subsequent
removal
of the Mask bit will allow that interrupt to
pass through to the IBM Personal Computer.
Scan Code Register (2DS)
This 8-bit register is internal to the emulation adapter and is set
and reset by the IBM Personal Computer. This register requires
one address.
In 3278/79 Emulation mode, this register is used by the IBM
Personal Computer to send a keystroke code to the control unit.
The IBM Personal Computer will
not change the contents of this
register if bit 3
of the Control Register is set.
Note: The scan code placed in this register must be the
ones-complement
of the data to be sent to the control unit.
1-9

Terminal ID Register (2D6)
This 8-bit register is internal to the emulation adapter and is set
and reset
by the IBM Personal Computer. It requires one
address.
This register must
be set by the IBM Personal Computer before
enabling the coaxiallin1c
Note: The Terminal ID placed in this register must be the
ones-complement
of the data to be sent to the control unit.
1-10

MemoryAddress Locations
There are 8KB of RAM reserved for the emulation adapter. The
beginning address
is CEOOO; the ending address is CFFFF.
Base Address Low Address
Hex Bits
Register
CEOOO -Starting address PC Address bits 12-0 RAM Data
Memory Address Locations
1-11

Accepted Commands
Below is a list of the commands sent from the control unit and
recognized by the IBM Personal Computer 3278/79 Emulation
Adapter Card.
Note: The emulation adapter will respond
to all good
transmissions.
Coaxial
Frame Bits
Commands
56789
READ Poll (include priority) o0 0 0 1
Read Data
o0 0 1 1
Read Address Counter High
00101
Spare
o0 1 1 1
Read Terminal ID o 1 0 0 1
Read Multiple
o 1 0 1 1
Read Status o1 1 0 1
Spare
o 1 1 1 1
Poll Acknowledge
1
000
1
Spare
1 0 0 1 1
Read Address Counter Low
1 o 1 0 1
Spare
1 o1 1 1
(Part 1 of 2) Accepted Commands
1-12