ACT apricot Product manual

~~ · apricot
\) ~~ o
Technical Reference
Manual

apricot
Technical
Reference Manual

COPYRIGHT
Portions of this manual contain material reprinted by
permission of:
SONY Corporation, Copyright 1982.
TRADEMARKS
MicroScreen is a registered trademark ofACT.
MS is a registered trademark of the Microsoft
Corporation.
CP 1M is a registered trademark of Digital Research.
IBM is a registered trademark of International Business
Machines.
ACKNOWLEDGEMENTS
ACT wish to acknowledge the invaluable assistance afforded
by its consultants inbringing Project Apricot to fruition.
QED Project Design,
Clarence House,
Newport, Gwent.
CAPA,
Aberdeen House,
Highbury Grove,
Islington,
LondonN2.
Information contained in this document is subject to
change without notice and does not represent a
commitment on the part of ACT.
All rights reserved, no use or disclosure without
written consent.
Copyright © 1983 ACT (International) Limited,
ACT House, III Hagley Road, BirminghamB16 8LB.

The Technical Reference Manual for the ACT Computer
Apricot is divided into three sections and a number of
appendices, as detailed below. This manual is intended for
programmers
and engineers involved in hardware and
software design for Apricot.
l.SYSTEM OVERVIEW
This section provides an overall description of the Apricot
computer and is divided into three chapters:
1-1 HARDWARE, describes the hardware of Apricot in
its basic configuration, and forms the introduction to
the three elements which constitute the
microcomputer;the System Unit,the Keyboard Unit
and the Display Uni t.
1-2 SOFTWARE, provides a brief description of the
operating system and its interface to the associated
BIOS. An introduction to the software modules which
constitute the BIOS is also provided.
1-3 OPTIONS, forms the introduction to the hardware
options available for the microcomputer, at the time of
printing the manual.
2.HARDWARE DETAIL
This section contains detailed descriptions of all the
hardware aspects of the microcomputer and is divided into a
number of chapters, as detailed overleaf. Each of the three
elements of Apricot are discussed in detail with major
circuit elements (e.g. Disk Drives, Power supply etc.) also
having separate descriptions.

3.S0FTWARE DETAIL
This section contains a detailed description ofall
software aspects of
the BIOS and is also divided into a
number of chapters. The first provides a detailed description
of
the BIOS as a whole with subsequent chapters detailing
the individual hardware drivers.
APPENDICES.
A number of appendices are included in this manual
which provide general hardware reference information and
also associated software
information of specific use to
systems/ application programmers.

SECTION I.SYSTEM OVERVIEW
1-1 HARDWARE
CONTENTS ............................................................... 1
INTRODUCTION ..................................................... 1
SYSTEM UNIT .............. ... .......................................... 3
KEYBOARD UNIT ............. ... ..................................... 5
DISPLAY UNIT .......................................................... 7
1-2 SOFTWARE
CONTENTS ............................................................... 1
INTRODUCTION ..................................................... 1
BIOS FEATURES-
OVERVIEW OF CAPABILITIES ................................ 2
Foreground and Background Operations ............... 2
Multi -sector Reads and Writes .............................. 3
Tri -buffer ... ... .... .. .. .. .. .. .... .. .. ... .. .... .. .... .. ................... 3
Apricot Control Device .......................................... 4
System Configuration Block .................................. 4
MicroScreen Driver ................................................ 4
Time and Date Clock ............................................. 5
Calculator ............................................................... 5
General Hardware Support .................................... 5
1-3 OPTIONS
CONTENTS ............................................................... 1
INTRODUCTION ..................................................... 1
FLOPPYDISK OPTIONS ........................................... 1
128KBYTERAMEXPANSIONBOARD .................. 2
MODEM ..................................................................... 2
NUMERICDATAPROCESSOR ............................... 3

CONTENTS
SECTION 2.HARWARE DETAIL
2-1 SYSTEM UNIT
CONTENTS ............................................................... 1
INTRODUCTION ..................................................... 1
SYSTEM BOARD ........................................................ 2
DISK DRIVES ............................................................. 3
POWER SUPPLYDETAILS ....................................... 3
General ................................................................... 3
DC Supply Distribution ......................................... 4
Fuse Rating ............................................................. 4
PHYSICAL DIMENSIONS ........................................ 5
2-2 SYSTEM BOARD
CONTENTS ............................................................... 1
INTRODUCTION .........:........................................... 1
DESCRIPTION ..... ... ................................................... 1
Processors .......................................................,
., ., ., . 1
Communications Handling ................................... 2
Sound Generation .................................................. 3
System Memory ..................................................... 3
CRT Controller ...................................................... 4
Floppy
Disk Controller .......................................... 4
Expansion Slots ...................................................... 4
Interrupt Controller ............................................... 4
Timer ...................................................................... 4
Input/Output Space ................................................ 5
2-3 INTERRUPT CONTROLLER
CONTENTS ............................................................... 1
INTRODUCTION .................................................. ... 1
DESCRIPTION ........................................................... 3
General ................................................................... 3
Interrupt Sequence ................................................. 4
Interrupt Masking .................................................. 5
PROGRAMMING CONSIDERATIONS .................. 5
General ..............................................."'................... 5
Initialization Command Words ............................. 6
Operational Command Words ............................... 8

CONTENTS
2-4 TIMER
CONTENTS ............................................................... 1
INTRODUCTION ..................................................... 1
DESCRIPTION ........................................................... 2
General ................................................................... 2
Counter 0 ................................................................ 5
Counter 1 and 2 ...................................................... 6
Baud
Rates .............................................................. 8
2-5 CRT CONTROL
CONTENTS ............................................................... 1
INTRODUCTION ..................................................... 1
DESCRIPTION ........................................................... 2
General ................................................................... 2
Mode Selection ....................................................... 8
CRTCDETAIL .................,...................................... 10
General ................................................................ 10
Register Description ........................................... 13
Initialising the CR TC ... ...... .. .. ....................... .. ... 16
CR TC Connections ............................................. 17
SCREEN RAM ......................................................... 19
General ................................................................ 19
Text Mode ............................................................ 20
Graphics Mode .................................................... 22
SYSTEM RAM UTILISATION ............................... 23
General ................................................................ 23
Text Mode ............................................................ 24
Graphics Mode .................................................... 25
DISPLAY UNIT CONNECTOR DETAIL ............. 26
2-6 FLOPPY DISK INTERFACE
CONTENTS ............................................................... 1
INTRODUCTION ..................................................... 2
DESCRIPTION ........................................................... 4
General ................................................................... 4
Disk Write .............................................................. 5
Disk Read ................................................................ 5
Disk Formatting ..................................................... 6
Read/write Head Positioning ................................. 8

CONTENTS
"-.
FDC DETAIL .............................................................. 9
General ................................................................... 9
ProcessorInterface ...... .. .. .. .................................. 10
Disk Drive Control ............................................. 13
Command Register ............................................. 14
Status Register ..................................................... 15
Track Register ..................................................... 15
SectorRegister ..................................................... 15
Data Register ....................................................... 16
PROGRAMMING CONSIDERATIONS ............... 16
Disk Drive Selection ........................................... 16
Head Loading ....................................................... 16
Head Positioning ................................................. 17
Data Transfers ..................................................... 21
Formatting Commands ....................................... 26
Force Interrupt Command .................................. 32
INTERFACE CONNECTION DETAILS ............... 33
System Connections ........................................... 33
Disk Drive Connections ..................................... 35
TRACKFORMAT ................................................... 37
2-7 SERIAL INTERFACE
CONTENTS ............................................................... 1
INTRODUCTION ..................... ... ............................. 1
DESCRIPTION ........................................................ ... 3
General ................................................................... 3
SIO Overview ......................................................... 4
SIO Architecture .................................................... 6
ProcessorInterface .............................................. 10
Write Register Definition ................................... 11
Read Register Definition ..................................... 25
SIO Interrupt Sequence ....................................... 30
KEYBOARD COMMUNICATIONS ...................... 32
General ................................................................ 32
Keyboard Connector Detail ................................ 33
Channel B Programming Details ........................ 34
PARALLEL INTERFACE INTERRUPTS ............... 36
RS232CCOMMUNICATIONS ............................. 37
General ................................................................ 37
RS232C Connector Detail .................................. 38
Channel A Programming Details ....................... 39

CONTENTS
SIO PIN DETAIL ..................................................... 42
System Connections ........................................... 43
Channel A Connections ...................................... 44
Channel B Connections ...................................... 47
2-8 PARALLEL INTERFACE
CONTENTS ............................................................... 1
INTRODUCTION .. ............................. ... ................... 1
DESCRIPTION ........................................................... 3
General ................................................................... 3
Printer Interface ...................................................... 4
System Control Interface ....................................... 6
2-9 SOUND GENERATION
CONTENTS ............................................................... 1
INTRODUCTION ..................................................... 1
DESCRIPTION ..................................... ... ................... 2
General ................................................................... 2
Tone Generation .................................................... 4
Noise Generation ................................................... 6
2-10 EXPANSION SLOTS
CONTENTS ........:...................................................... 1
INTRODUCTION ..................................................... 1
DESCRIPTION ........................................................... 3
Electrical Specification .......................................... 3
Pin Detail .. .. ................. .. .. .. .. ..... .. .. .......................... 5
Address Allocation .............................................. 10
Expansion Board
Layout Detail.......................... 10
2-11 DISK DRIVE
CONTENTS ............................................................... 1
INTRODUCTION ..................................................... 1
DESCRIPTION ........................................................... 2
- General ................................................................... 2
Interface
Connections ............................................ 3
Disk Drive Mechanism .......................................... 7
Read/Write Head .................................................... 7
Head Positioning Mechanism ................................ 7

CONTENTS
Head Load Mechanism ........................................... 7
Sensors
and Detectors ............................................ 8
Drive Switch Settings ............................................ 8
Drive Specification ................................................. 9
DISKS ....................................................................... 10
General ................................................................ 10
Disk Precautions ................................................. 11
Disk Insertion/Removal ..................................... 12
Write Protecting .................................................. 12
Disk Format ......................................................... 12
2-12 KEYBOARD
CONTENTS ............................................................... 1
INTRODUCTION ..................................................... 1
SERIAL LINK CONTROL AND FORMAT .............. 2
KEYSWITCH OPERATION ...................................... 3
MICROSCREEN OPERATION ................................. 4
CLOCK OPERATION ................................................ 6
MOUSE PORT OPERATION .................................... 7
KEYBOARD FIRMWARE .......................................... 8
Keyboard to System Unit Character Codes 10
System Unit to Keyboard Character Codes ........ 11
2-13 DISPLAY UNIT
INTRODUCTION ..................................................... 1
DESCRIPTION ........................................................... 1
General ................................................................... 1
Physical Dimensions ............................................. 2

CONTENTS
SECTION
3.S0FTWAR~ DETAIL
3-1 PROGRAMMERS GUIDE TO THE BIOS
INTRODUCTION ..................................................... 1
BIOS Internal Structure - Memory Map .................. 1
VECTORS ................................................................... 3
POINTERS .................................................................. 3
CHARACTER FONTS 1, 2 and 3 .............................. 4
SECONDARY CACHE .............................................. 5
PRIMARYCACHE ..................................................... 5
SYSINIT ...................................................................... 5
BIOS CODE ................................................................. 5
BIOS CONSTANTS ................................................... 5
GLOBALDATAAREA .............................................. 6
BIOS HEAP AND STACK .......................................... 6
MS-DOS 2.00 .............................................................. 6
USERRAM ................................................................. 6
3-2 SCREEN DRIVER
INTRODUCTION ..................................................... 1
APPLICATIONS INTEREST .... ... .............................. 1
Escape
Sequence Management Functions ............. 1
Environment Flags ................................................. 8
ANSI Escape Sequences ......................................... 9
Physical Screen Layout ....................................... 12
Reverse FieldVideo .............................................
13
High/Low Intensity ............................................. 13
Underline ............................................................. 13
Strikethrough ...................................................... 13
Software Reserved ............................................... 13
Character Font-cell ............................................. 14
SYSTEMS INTEREST ............................................. 15
CRTC Initialization ............................................ 15
Low-level Display routines ................................. 15
Cursor management routines ............................. 15
How a character appears on the screen ............... 16

CONTENTS
3-3 MICROSCREEN DRIVER
INTRODUCTION ..................................................... 1
APPLICATIONS INTEREST ..................................... 1
SYSTEMS INTEREST ................................................ 4
3-4 KEYBOARD DRIVER
INTRODUCTION ..................................................... 1
APPLICATIONS INTEREST ..................................... 1
Keyboard Look-up table ......................................... 1
SYSTEMS INTEREST ................................................ 4
Keyboard to Apricot Handler ................................. 4
Key
Make Code handler ......................................... 5
Key Break Code
handler ......................................... 7
Translation of data routines ................................... 8
Auto Repeat handler .............................................. 8
Non make/break code interpreter ......................... 8
Queue handlers for data to MS-DOS ..................... 9
MS-DOS queue ....................................................... 9
Local queue ............................................................. 9
Keyboard
queue ................................................... 10
3-5 CONTROL DEVICE DRIVER
INTRODUCTION ..................................................... 1
APPLICATIONS INTEREST ..................................... 1
Calling the control device ...................................... 1
Specification of the Apricot Control Device ......... 3
Screen Driver .......................................................... 3
Keyboard
Driver ..................................................... 3
MicroScreen Driver ................................................ 5
Serial Port Driver .................................................... 6
Parallel I/O Driver ............................................... 12
Sound Generator ................................................. 14
Floppy
Disk Drivers ............................................ 15
Cache/Graphics/IBM configuration ................... 16
SYSTEMS INTEREST ............................................. 17

CONTENTS
3-6 DISK INPUT/OUTPUT SYSTEM
INTRODUCTION .. ................................................ ... 1
APPLICATIONS INTEREST ..................................... 1
SYSTEMS INTEREST ................................................ 1
Disl< Format ............................................................ 2
The Label Sector ..................................................... 3
MS- DOS AND BIOS UTILISATION OF THE
DISKS .......................................................................... 4
FAT's 1
and2 .......................................................... 4
Directory ...........................;..................................... 4
Character Font ........................................................ 4
Keyboard table ........................................................ 5
SYSINIT .................................................................. 5
BIOS code ................................................................ 5
MS-DOS 2.0 ............................................................ 5
Configuration data ................................................. 5
3-7 BOOT ROM
INTRODUCTION ..................................................... 1
APPLICATIONS INTERST ....................................... 1
Software Reset ........................................................ 1
Logo display ............................................................ 1
3-8 CALCULATOR
INTRODUCTION ..................................................... 1
APPLICATIONS INTEREST ..................................... 1
SYSTEMS INTEREST ................................................ 2
3-9 SOUND GENERATION
INTRODUCTION ..................................................... 1
APPLICATIONS INTEREST ..................................... 1
3-10 AUXILIARY DEVICE/SERIAL PORT
INTRODUCTION ..................................................... 1
APPLICATIONS INTEREST ..................................... 1
SYSTEMS INTEREST ................................................ 1
Modem Control Through the AUX Device ........... 2

CONTENTS
3-11 GRAPHICS SYSTEM EXTENSION SYSTEM
INTRODUCTION ..................................................... 1
APPLICATIONS INTEREST ..................................... 1
Graphic System Extension Functions .................. 1
How to use Graphic Systems Extension ............... 1
What is Graphic System Extensions? .................. 2
SYSTEMS INTEREST ................................................ 2
GRAPHICS.EXE ..................................................... 2
ASSIGN.SYS ........................................................... 3
DDACRT.SYS ........................................................ 3
ACT GRAPHICS SYSTEM -DDACRT.SYS ......... 3
APPENDICES
CIRCUIT DIAGRAMS ...................................................... A
BOOT PROM DIAGNOSTICS ......................................... B
DEFAULTCHARACTERFONT ..................................... C
HEXADECIMAL
TO DECIMAL CONVERSION .......... D
DESIGN CRITERIA FOR THE EXPANSION SLOTS ..... E

SECTION 1:
SYSTEM OVERVIEW
HARDWARE .................................................................. 1-1
SOFTWARE .................................................................... 1-2
OPTIONS ........................................................................ 1-3

List of Contents Page
INTRODUCTION .......................................................... 1
SYSTEM UNIT ............................................................... 3
KEYBOARD UNIT ......................................................... 5
DISPLAY UNIT .............................................................. 7
List of Illustrations
Figure
Apricot
Computer ........................................................... 1
Apricot
Computer block diagram .................................. 2
INTRODUCTION
The Apricot is the generic name given to a family of
16-bit
microcomputers, possessing a diverse range of
hardware facilities
to suit the needs and requirements of the
user in a wide variety of applications. Each member of the
family is produced starting from an Apricot in its basic
operational configuration.
This is then transformed into a
different
member of the family by the addition of options, as
required. A
more detailed treatment of the optionsis
provided
in a subsequent chapter.
All Apricot
computers are composed of three separate
elements; a
System Unit, a Keyboard Unit and a Display
Unit as illustrated on Figure 1.
The System Unit is the area of the computer, which
houses the majority of the processing elements, the system
memory components and the interface circuitryfor
peripheral
equipment. The Unit also contains the following
items:
(a) At least one micro floppy disk drive.
(b) A power supply module.
(c) A loudspeaker.
(d) A coolingfan.

HARDWARE
The Keyboard Unit consists of, a standardlayout
typewriter keyboard, a calculator keypad, a number of
programmable
function keys with associated LED
indicators, a
set of "fixed" function keys, and a 2 line by 40
characterMicroScreen. The Keyboard Unit also contains
processing
circuitry which provides the interface between
the keys and the System Unit.
The standard Display Unit is a high resolution 9 inch
monochrome display which fits into a shallow recess on the
top of the System Unit. The Display Unit tilts, swivels and
slides, enabling
the operator to position the screen to obtain
the optimum viewing angle. An anti-reflective mesh is
incorporated
on the screen to minimise the possibilityof
eyefatigue.
In
its basic configuration, the Apricot Computer
incorporates the following:
(a) An Intel 8086 16-bitprocessor.
(b) An Intel 8089 16-bit input/output processor.
(c) 256 Kbytes of dynamic RAM.
(d) A single3.5 inch MicroFloppy disk drive.
(e) A Centronics parallel port for connectinga printer.
(f) An RS232C serial interfacefor data
communica tions.
(g) A port for connecting a "mouse" device.
(h) A sound generator to provide audiofeedback.
(i) Two internal expansion slots to cater for RAM
expansion
and connecting other optionalfacilities.
(j) A port for connecting a light pen plusassociated
ancillary electronics.
The basic configurationof the microcomputer canbe
expanded by
the addition of two further options, in addition
to the optional facilities available via the internal expansion
slots.
These two further options are as follows:
(a) A second3.5 inch MicroFloppy disk drive.
(b) A numeric data processor (Intel 8087) to increase
the processingcapabilities of the microcomputer in
mathematical and scientificapplications.

HARDWARE
Connections for the printer, data communications
equipment and mains input are located at the rear of the
System Unit, together with connectors for the Keyboard and
Display Units. The expansion slots and the connection for
the light pen and associated circuitry are located within the
System Unit. The connection for the "mouse" device is
located
at the rear of the Keyboard Unit.
SYSTEM UNIT
All the processing and control circuitry within the
System Unit is contained on a single printed circuit board,
designated
the System Board, which is'fitted horizontally
inside the System Unit housing. The major elements of the
System Board are illustrated on the block diagram, Figure
2a/2b.
The System Board incorporates the following items:
(a) The system processing elements.
(b) The Boot PROMs.
(c) 256 Kbytes of DRAM.
(d) A floppy disk controller.
(e) A parallel printer interface.
(f) A dual channel serial interface, one channel for the
Keyboard and the other for the RS232C connector.
(g) A display controller.
(h) Two expansion slots.
The processing elements on the System Board are
arranged
in a multiprocessing configuration which includes
two Intel16-bit microprocessors; an 8086 central processing
unit (CPU) and an 8089 input/output processor (lOP). The
two microprocessors are connected in parallel and sharea
common bus structure. This configurationis termed (by
Intel), a local
multiprocessing configuration. The number of
microprocessors within the local multiprocessing
configuration is increased to three if the optional lntel8087
numeric data processor (NDP) is fitted.
In the local multiprocessing configuration, only one of
the microprocessors has access to the sharedaddress,
control and data buses at anyone time. The input/output
processoris employed to perform the bulk of routine data
transfers, under the direction of the central processing unit.

· HARDWARE
High speed DMA data transfers, from a selected source
(memory or peripheral) toa selected destination (memory or
peripheral), are performed by the lOP. The lOP is able to
transfer data whilst the central processing unit is engaged in
executing tasks which do not require use of the buses.
The 8087 numeric data processor extends the processing
capabilities of the Apricot computer, by performing
arithmetic and comparison operations on numeric types
which can vary from 16 to 80 bits. It is also able to execute
numerous transcendental functions (e.g.tangent and
logari thmic functions).
- The Apricot computer uses 3.5 inch Sony disk drives and
employs the IBM system 34 format in the double density
mode, with 512 bytes per sector (and 9 sectors per track).
The total storage capacity of each disk is 315 Kbytes of
formatted data. The floppy disk controller incorporates the
necessary capability to control a second floppy disk drive
without any modification to the hardware.
The serial interface provides two separate channels; one
channel for communication between the System Board and
the Keyboard Unit; the second channel for communication
between the System Board and data communications
equipment. The serial link to the keyboard is a full duplex
asynchronous communications channel, which transmits
and receives data at a fixed baud rate.
The RS232C channel can be programmed to operate in
both asynchronous and synchronous modes, with the
programmer having independent control over transmit and
receive baud rates. The rates can be generated by either an
internal programmable timer or determined by the external
data communications equipment. Both byte and bit
oriented synchronous modes are available. These include
the byte oriented modes, Monosync and Bisync, and the bit
oriented modes, SDLC ana HDLC.
The two expansion slots are identical and allow the basic
configuration of
the computer to be expanded by the
addition of optional expansion cards. The expansion bus
consists of the processing system buses (address, control