NCR PC4I Use and care manual

Personal
Computer
PC4i
Technical Reference
Manual

GW-BASIC is a trademark of Microsoft Corporation
January 1986
Copyright '~ ' 1985, 1986 by NCR Corporation
Dayton, Ohio
All Rights Reserved
Printed in
the Federal Republic of Germany
(
It is the policy of NCR Corporation to improve
products as new technology, components, software, and
firmware become available. NCR Corporation,
therefore, reserves the right to change
specifications without prior notice.
All features, functions, and operations described
herein may not be marketed by NCR in all parts of the
world.In some instances, photographs are of equipment
prototypes. Therefore, before using this document
consult your dealer of NCR office for information
that is applicable and current.

(_
INTRODUCTIOR
YOUR RCR PEBSORAL COMPUTER HODEL 41 AND fflIS HARUAL
Your NCR PERSONAL COMPUTER MODEL 4i is a powerful
business/professional personal computer. It is
designed to act not only as an independent, self-
sufficient system, but also as a control center for
systems fulfilling a wide range of business,
scientific and technological requirements.
Essential electronics are contained on the controller
board. Where possible, LSI components have been used,
providing compactness and a high degree of
reliability. The microprocessor is the 8088, which
can be supplemented by the 8087 co-processor, if
required. With the additional support of Direct
Memory Access, high processing speeds can be
achieved. 256 Kilobyte of random access memory are
included in the standard version, over and above
video RAM.
The NCR PERSONAL COMPUTER MODEL 4i is equipped with
Centronics and RS-232-C interfaces as standard. These
are accessed at the rear of the computer without any
dismantling. Full access to the system bus is
available at the internal expansion card assembly.
This assembly can accomodate up to seven cards to
expand the features of your system. One additional
monitor can be connected via an expansion card, so
that the computer can drive a monochrome and a color
display simultaneously.
The NCR PERSONAL COMPUTER MODEL 4i is operationally
compatible with a number of other widely used
personal computers. This provides for portability of
a large number of software applications and hardware
extensions between your NCR PERSONAL COMPUTER 4i and
other personal computers you may have occasion to
use. In addition, your NCR PERSONAL COMPUTER 41
offers the advantages of single cabinet design, an
extended keyboard, and an excellent high-resolution
display in conjunction with a color CRT,

This Manual, consisting of two volumes, is intended
for designers, system integrators, and programmers
who require detailed information about the
construction and operation of the NCR PERSONAL (
COMPUTER MODEL 4i. Volume 1 includes information
about the I/0 bus, signal levels and timing, power
requirements, and pin assignments, not only of the
NCR PERSONAL COMPUTER MODEL 4i itself, but also of
the kits available from NCR. In addition, details are
given about low-level software control of hardware
functions. Volume 2 provides full schematics.
Assembly language listings of the NCR ROM BIOS are
also available as a separate document.
The
NCR PERSONAL COMPUTER MODEL 4i is optionally
available in a version for use with the Videotex
information and communication system. Videotex is
administered under the auspices of the post and
telecommunications authorities of a number of
countries. The Videotex version of the NCR PERSONAL
COMPUTER MODEL 4i is described in a Chapter of its
own in this Manual.
With the help of the information contained in this
Manual, you may be intending to make hardware or
software changes to the NCR PERSONAL COMPUTER 4i for
specialized use. Because of the complex nature of
computer technology, we must stress that NCR cannot
accept responsibility for problems arising from such
changes. At the same time, we are constantly
endeavoring to maintain the quality of information
provided in this Technical Reference Manual.
Therefore, if you find that there is a particular
aspect of information not already provided in this
Manual, or if you want to let us know how useful you
find it, please ask your supplier to forward your
comments to us.

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NCR PERSONAL COMPUTER MODEL 4i
TECHNICAL REFERENCE
MANUAL
CONTERTS
CHAPTER 1: System Overview
Models and Options ••.••••••••••.•••••••••••••• 1-1
Model
Identification •••••••..••••••••••••••••• 1-4
System Components . . . • • • . • . . . . . . . • . . • . • . . . • • • . . 1-5
System Connection •••••••••••••••••••••••••••• 1-12
I/0 Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-12
Rack Assembly • . . . . . • • . . . • • . . . • . . . • . • . . . . . . • 1-15
Configuration Switches ••••••••••••••••••.••.• 1-16
Memory Expansion • . . • • • • • • • • • . . . • . • • . • • . . . • . . . 1-18
Memory Map • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • . • • • • 1-1 9
I/0 Map ••••••••••••••.••••••••••.••.••••••••• 1-21
Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-22
Monochrome Systems •••••••••••••••.••••••••• 1-22
Color Systems .............................. 1-23
Specifications •.........•.•.................. 1-25
Alternate Main Processor Board ••••.•••••••••• 1-26
CHAPTER 2: Programmable Intelligence
8088/8087 Co-ordination ••••••••••••••••••••••• 2-3
Programmable Interval Timer •••••••••.•••.••..• 2-4
Hardware Configuration •••••••••••••••••••••• 2-4
Timer Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
Output on Terminal Count (Mode 0) ••••••••• 2-6
Programmable One-Shot (Mode 1) •••••••.•••• 2-7
Rate Generator (Mode 2) ••••••••••••••••••• 2-7
Square Wave Generator (Mode 3) •..........• 2-7
Software Triggered Strobe (Mode 4) •••••••• 2-7
Hardware Triggered Strobe (Mode 5) •••••••• 2-8
Timer Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9
Reading the Counters •••••••••••••••••••••• 2-9
i

Programmable Interrupt Controller (PIC)
Introduction .............................. .
Why use Interrupts? •••••••••••••••••••.••
Interrupts and the 8088 Microprocessor ••.
Interrupt Controller Hardware and Logic
Programming
the PIC ••.•.••••••••••••.••
Initializing the PIC .••.•••••••••••••.•.•
Operation Command Words ••.•••..•.•••.....
Signal Integrity
System Interrupts ......................... .
Interrupt Handling: Examples •••...•••...•••
Parallel Input/Output Interface •••••••.•••..•
Programming the 82 55A .•••.••••••••••••..•.
Mode 1
Mode 2
Mode 3
8255A: System
Use
Direct Memory Access
System Integration ........................ .
8237 Registers
Command Register
Mode Register ........................... .
Request Register ........................ .
Mask Register ......................... .
Status Register ......................... .
Temporary Register ••••••.••.•••.•..•.•...
Current Address Register ...••..•.•.•.•...
Current Count Register .•••.••••.•••.••..•
Base Address and Base Count Registers
DMA Timing ..••.••......•....•..............
8237: System Use
RAM Refresh •••••••.•.•.••.•••.•.•••••••..
Flexible Disk DMA Service
DMA Page Selection •.•••..••.•••.•••••••••
CHAPTER 3: The Operating System
ii
Introduction .......................... .
ROM BIOS
BIOS Data Areas
System
Initialization
2-10
2-10
2-10
2-11
2-12
2-13
2-16
2-19
2-26
2-26
2-28
2-42
2-42
2-43
2-44
2-46
2-48
2-50
2-50
2-54
2-56
2-57
2-58
2-59
2-59
2-60
2-60
2-60
2-61
2-61
2-64
2-64
2-66
2-68
3-1
3-3
3-18
3-24

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0
(,
CHAPTER 4: Printers and Communications
Introduction ••..••••••••..•••••.•••••••••••••• 4-1
RS-232-C
Input/Output •••.••.•••.••.•••.••••••• 4-1
Programming
the Serial Receiver/Transmitter. 4-6
Interrupt Enable Register ••.••.••••••••••• 4-9
Interrupt ID Register •••••••••.•••.•••••• 4-10
Line Control Register •••••..•.•..•.••••.. 4-10
Modem Control Register ••••••••••••••••••• 4-11
Line Status Register ••••••••••••••••••••• 4-11
Modem Status Register ••••••••••••••.••••• 4-12
Internal Diagnostics .•.••••.••••••••.•••••• 4-12
Data Integrity .••••••••.•••.••••••••••.•• 4-13
The Interrupt System • . . • • •• . . • • •. • . • ••. • • 4-1 3
Receiver/Transmitter Timing •••••••.•.•••••. 4-14
Baud
Rate Selection ••••..•••••.•.•••••••••• 4-17
Programming
Hints .••••••••••••••••••••••••• 4-18
Interface Availability ••••••.•.•••••••••• 4-18
Initialization ................•.......... 4-18
Transmit ting Data • . . •. •. •• • • •• •• •• • • •••. . 4-20
Receiving Data ........................... 4-21
Centronics Interface •••••••.••...•••••••.•••• 4-24
Software Control ••••.•••••.•••••••••.•••••• 4-27
Status And Control Registers .••••••••••.• 4-27
Centronics Printer Control ••••••••••••••• 4-28
Printer Status Analysis ••••...•.••••••.•. 4-29
CHAPTER 5: Inhouse DLC Inter~ace
Interface Connections •••.••.•••.••••••••.••••••• 5-1
DLC Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2
Controller Pin Configuration •••••••••••.•••••• 5-2
Software Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6
Command Register ••••.••.•••.••••••••.••..••• 5-7
Status Register ••••••••••••••••••..••••••••• 5-8
Interrupt Status Register ••••••..•••••••••• 5-10
Unique Address
Register ••••••.••••.•••••••• 5-10
Programming Considerations ••••••••••••••••.•• 5-11
Transmitting via CPU ••••••••••••••.••••.•.• 5-11
Receiving via CPU •••.•••••••••••••••••••.•. 5-13
Transmitting via DMA .••••••••.•••••••••.•.. 5-15
Receiving via DMA ••••••••••••.••••.•.•••••• 5-17
iii

CHAPTER 6: Disk Storage
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1
48TPI Flexible Disk Drive ••.••.•••••••••••••.• 6-1
Control and Data Signals •••••••••••••••••••• 6-4
Minimum Format Requirements .••••.••••.•••.• 6-13
Flexible Disk Controller ••••.••••••.•.••••• 6-15
Main Status Register •••..•.•••.•••••.•••• 6-16
Disk
Select Register •••••••••.•••.••••••• 6-18
FDC Commands and their Parameters .••.•••. 6-18
Motor On/Off ......................•...•.. 6-39
FDC Status •••••••••••••.••••••••••••.•••• 6-39
Fixed (Winchester) Disk Drive ••••.••••••.•••. 6-46
Control and Data Signals •.••••••••••••••••• 6-48
Fixed Disk Controller ••••.••••••••••••••••• 6-56
Programming
the Fixed Disk Controller •••• 6-58
Fixed Disk Controller Status ••••••••••..• 6-64
Fixed Disk Controller Diagnostics •••.••.• 6-66
Fixed Disk Format •••••••••••••••••••••••• 6-67
External Fixed Disk Connection ..••••.•••••• 6-68
1.2 MB Flexible Disk Drive •.••••••••••••.•••• 6-69
CHAPTER 7: The Screen Display
Available Adapters •. • • •. • •• . • ••• • . . • • . • . •. • • •. 7-1
Connection and Configuration .•.•..••••••.••••• 7-2
Character Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4
Monochrome Character Display •••.•.••••..•.••• 7-23
Character Display Memory ••..••••••••••.•••• 7-27
Character Display Controller ••..•••••••.•.. 7-28
Character Cursor •••••••••.•.••.••.•.••••••. 7-31
Color Graphics Display .•••••..••••••••...•••. 7-32
Graphics Display Memory .••.••.•...••••.••.. 7-36
Graphics Display Controller •••••••.•••••••• 7-36
Character Mode ..•.......................... 7-38
Graphics Modes ............................. 7-40
Low Resolution ........................... 7-40
Medium Resolution ........................ 7-44
High Resolution •••..•••..••••..•••••.•••• 7-45
Graphics Cursor ............................ 7-63
Controller Data Conversion ••••••.••.•..•••• 7-63
iv

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CHAPTER 8: The Keyboard
Keyboard Performance
Code Generation •••••
Diagnostics
CHAPTER 9: The Loudspeaker
8-10
8-10
8-12
Hardware Characteristics •••••••••••••••••••.•• 9-1
Programming Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1
CHAPTER 10: Videotex
Introduction ••••••••
10-1
Switches and Connections • . . . . . . . . . . . . . . . . . . . . 1 0- 3
Monitor Connection
Modem and VLP Connection •••••••••••••••••••
Switches
10-4
10-4
10-7
Videotex Memory Organization ••••••••.•••••.•• 10-9
Display Generation •••••••.••••••••••••••••.•
Videotex Controller •••••••••••••••.•••••••
Character Sets
10-11
10-11
10-12
Standard Characters ••••••••••••••••••••. 10-12
Definable Characters •••••.•••••••••••••• 10-17
Character Attributes
.................... 10-28
Color Selection .......................... .
Color Layers
Color Coding
Color Look-up Table •••••.•••••••••••••••
DRCS Attributes
Transparency ........................... .
Videotex Controller Registers •••••••.•••••••
Scroll Map Registers ••••••••••••••••••••••••
Scrolling ................................ .
10-31
10-31
10-32
10-33
10-33
10-34
10-35
10-40
10-40
Text Display and RAM Access
NCR Software
. . . . . . . . . . . . . . . 10-41
Printing Videotex RAM •••••••••••••••••••••••
.........................
10-42
10-49
10-50
RS-232-C
Interfaces
RS-232-C Software Control
. . . . . . . . . . . . . . . . . 10-5 1
PCI Receiver
............................
PCI Transmitter ........................ . 10-51
10-52
V

Modem Interrupts • . •• • • • •. • •• • •• • •• •• •• . • 10-53
Programming
the PCI • . . • . . • • . •. . . •• . • • • • • 10-53
Programming Asynchronous
Communications. 10-56
Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-57
Status Register •••.•••••..•••..•••••..•. 10-58
Adapter Initialization •• . . • ••••. . •• . • . • • •. . • 10-59
Modem Interface •.•••••••••••••••••.••••..• 10-59
Video
Interface ...•.•••••..••.•..•.•.•...• 10-61
Switches and Registers ••••••••••••.•..•••• 10-62
CHAPTER 11: Index
APPENDIX
A Hardware Rererence
(Includes own table of contents)
B The ROM BIOS
(Available as separate document)
vi

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Chapter 1
System Overview
MODELS AND OPTIONS
The NCR PERSONAL COMPUTER consists of a main display
unit and a keyboard. The computer is available in
different models and has a variety of options that
can be added to each model. Expansion boards from
non-NCR {"third party") manufacturers can be used
with the NCR PERSONAL COMPUTER, as well as expan-
sion boards offered by NCR,
The standard display unit is made up of the following
parts:
* Cabinet
*
*
Power supply
One or two flexible disk drive{s) or one
flexible disk drive and one hard disk drive
* 12-inch monochrome CRT display or 12-inch color
CRT display
* Main Processor Board with:
* 8088 Microprocessor
* 256 KB Random Access Memory {RAM)
* 16 KB Read Only Memory {ROM)
* RS-232-C Serial Interface
* Centronics Parallel Interface {for printer)
* Plug-in board option expansion slots
1-1

SYSTEM OVERVIEW
• Fixed disk drive controller plug-in board
for units with a hard disk drive.
• Video controller plug-in board.
A block diagram of the NCR PERSONAL COMPUTER hardware
is shown in Figure 1.1.
PQINER -
SUPPL V
~
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8
§
1
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16KB
8
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FLEX
DISK
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1-2
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6
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t_1J~7- K~00~1~1 _ _j
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CONTROL LE A 32KB
-1 l XPANSION 10 64 K8 I
113271 1(!,111 I
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Figure 1.1 Hardware Block Diagram
,-------,
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J IIF AQAPTE R I
113277 K1011 I
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,----------,
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IJ:184 K1401 I
.-------,1
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13784 1(1411
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- - · - - j

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SYSTEM OVERVIEW
The NCR PERSONAL COMPUTER is available in various
models. The standard internal RAM memory size for
all models is 256 KB. The models currently available
are:
* A 12-inch monochrome display, one flexible disk
drive and 256K memory
* A 12-inch monochrome display, two flexible disk
drives and 256K memory
* A 12-inch monochrome display, one flexible disk
drive and one hard disk drive, and 256K memory
* A 12-inch color display, one flexible disk drive
and 256K memory
• A 12-inch color display with two flexible disk
drives and 256K memory
• A 12-inch color display with one flexible disk
drive and one hard disk drive, and 256K memory
• A 12-inch color display with Videotex, one
flexible disk drive and 256K memory
* A 12-inch color display with Videotex, two
flexible disk drives and 256K memory
* A 12-inch color display with Videotex, one
flexible disk drive and one hard disk drive, and
256K memory
The
Videotex systems are dual purpose systems to be
used either as a Videotex system, or as a normal
personal computer, These systems are tailored to meet
individual country requirements, for example,
~ Bildschirmtext for Germany, Teletel for France, and
Prestel for Great Britain.
1-5

SY STEM OVERVIEW
MODEL IDENTIFICATION
The model number of the NCR PERSONAL COMPUTER is
stated on the plate at the back of the unit. The
meaning
of the model number is shown below:
3277-XX XX-XX XX
___ Language
____ Voltage/Frequency
______ Sub Model
_______ Maj or Model
_________ Class
The NCR 3277 model numbers are defined in Figure 1.2.
1-4
Major Model
Sub Model
Voltage/
Frequency
Language
11
12
NCR3'Z17
Monochrome CRT
Color CRT
13 Videotex CRT (Color)
01
02
Single Flexible Disk Drive
Duel Flexible Disk Drives
03 Herd end Flexible Disk Drives
71
73
DD
01
02
03
05
06
120 Volts, 50/60 Hz.
220/230/240 Volts, 50/60 Hz.
U.S. English
Int. English
U.K. English
Spanish
French
Germen
09
10
11
12
20
~edish
Deni sh
Norwegian
Itel ian
Finnish
Figure 1.2 Model Number Definition
(

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SYSTEM OVERVIEW
SYSTEM COMPONENTS
This section introduces elements of the NCR PERSONAL
COMPUTER shared by all models. Figure 1.3 provides an
easy-to-follow diagram illustrating the most
important components on the main processor board and
those external functions with which the main
processor board interfaces.
The CLOCK is the key to co-ordination of the entire
system. This unit consists of a crystal supplying a
signal of frequency 14.31 MHz to a Clock Controller.
The 8284A Clock Controller divides the frequency of
this input signal, in order to provide a suitable
timing signal (4.77 MHz) for the main system
microprocessor (CPU), as well as timing signals for
all the other system components.
The TIMER is an integrated circuit which can be
programmmed to produce a variety of signals at
various intervals. Accuracy is ensured by the Timer
deriving its synchronizing signals, by way of
suitable frequency division, from the system clock.
You can use the Timer for running a system clock of
your own, that is, a clock you can watch on the
screen. In addition, the Timer can be used to provide
the frequencies required if you wish to play music on
the computer. The Timer is also used for refreshing
random access memory (see below).
The CENTRAL PROCESSING UNIT (CPU), often simply
called "microprocessor", is widely acknowledged as
the most "influential" of the integrated circuits. It
is the CPU which passes on instructions supplied by
the programmer to the other units in the system.
Optionally, the CPU can be supported by the 8087 Co-
Processor. The Co-Processor is capable of performing,
in response to simple instructions, floating-point
calculations which would otherwise require extensive
programming of the CPU.
1-5

SY STEM OVERVIEW
The NCR PERSONAL COMPUTER makes use of two types of
memory: read only memory (ROM), and a large random
access memory (RAM) of at least 256 KB,
READ ONLY MEMORY contains instructions for the CPU
which enable the latter to get the system started, as
well as a "library" of short, but useful, programs
known under the collective term BIOS (Basic
Input/Output System). It is the task of the BIOS to
constantly maintain communication between the CPU and
the other system units.
RANDOM ACCESS MEMORY can likewise contain program
instructions for the CPU, but it is also used for
storing data being processed by the the program. The
random
access memory of your NCR PERSONAL COMPUTER is
"dynamic", which means that its contents can be
changed very quickly, thus providing for fast
processing. This also means that memory must be
"refreshed" at fixed intervals, to prevent its
contents from disappearing. Fortunately, you need not (_'
normally be concerned about providing refresh cycles,
as this is taken care of by the Timer,
The DIRECT MEMORY ACCESS (DMA) CONTROLLER is used for
the transfer of large blocks of data to and from
memory. DMA is particularly useful for reading data
from or writing data to flexible disk. The CPU does
not then have to specify a me•ory address for each
byte read or written. Instead, all the CPU has to
tell the OMA Controller is 1) that data is to be
transferred between memory and flexible disk, 2) the
address of the first byte in memory to be accessed,
and 3) the number of bytes to be transferred,
The I/0 CONTROLLER is used for reading the keyboard
and turning the loudspeaker on and off. In addition,
it keeps a note of the settings of system
configuration switches, so that programs can detect
the NCR PERSONAL COMPUTER model being used,
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C
C
(
SYSTEM OVERVIEW
The INTERRUPT CONTROLLER provides fast notification
of the CPU in the event that a system unit requires
urgent attention, This is especially important for
the Timer and keyboard: the Timer, because an
accurate clock (whether your own or provided by the
operating system) must not miscount the number of
ticks; the keyboard, because this is the most
expedient way for the user to intervene during
execution of a program.
Additional equipment can be interfaced via one or
more of the seven 62-pin I/0 connectors inside the
computer cabinet, One of these connectors is already
occupied by the board containing the controller
circuitry for the screen display,
With some personal computers, the three interfaces
marked with asterisks in Figure 1,3 (flexible disk,
parallel printer, RS-232-C) each require the use of
one of the six remaining connectors. The NCR PERSONAL
COMPUTER has the advantage that these three functions
are interfaced separately to the main processor
board, thus making these connectors available to
other options.
The system BUS provides the lines by which
communication between the units of the system can
take place. The bus really consists of three
busses, The address bus conveys memory or I/0 map
addresses by which memory bytes or external devices
can be accessed, Data is passed as parallel signals
on the data bus. Control bus is a collective term for
those signals which otherwise influence data flow
within the system, for example, signals which
determine whether the direction of data flow is read
or write, and whether transfer is to/from memory or
an I/0 device, Your NCR PERSONAL COMPUTER includes a
BUS CONTROLLER which relieves the CPU of such bus
arbitration duties, thus enabling the 8088
microprocessor to operate in its "maximum mode",
1-7

SYSTEM OVERVIEW
FLEX-DSK
CONTROLLER
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Figure 1.3 System Overview (1)
1-8

r
C
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SYSTEM OVERVIEW
Figure 1.4 provides a more detailed view of the
system. Busses are shown separately. Furthermore, a
number
of additional aspects are introduced.
NM! LOGIC determines what source of interrupt may be
allowed to issue the CPU non-maskable interrupt
(NMI). Possible sources are errors on I/0 and memory
transfers, and co-processor errors.
Bus transfer over a period of more than one clock
unit is enabled by the WAIT STATE LOGIC.
CHIP SELECT (CS) LOGIC converts address information
into CS signals for memory and I/0 interface
integrated circuits.
A DMA PAGE REGISTER allows DMA to address more than
64 KB of the memory address area.
PARITY CHECKING is performed during RAM access.
Finally, Figure 1.5 shows exactly where important
integrated circuits are situated on the main
processor board.
NOTE: Your NCR PERSONAL COMPUTER may include the
Alternate Main Processor Board which is
described in a separate section at the end of
this Chapter.
1-9

SYSTEM OVERVIEW
l
I
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1-10