RESEARCH MACHINES LINK 480Z User manual

LINK 480Z CASSETTE SYSTEM USERS GUIDE
PN
11684
Copyright ©1982, 1983 by Research Machines Limited
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rights reserved. Copies of this publication may be
made
by customers exclusively for their own use, but
otherwise no part of it may be reproduced, transmitted,
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translated
into any language or computer language without the
prior written permission of Research Machines Ltd.,
Post Office Box 75, Oxford, England. OX2 OBW Tel:
Oxford [phone].
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continuous development
and improvement of its
products and services, and the right is therefore
reserved
to revise this document or to make changes in
the products describes without notice. Research
Machines Limited endeavour
to ensure the accuracy of
this document
and to- ensure that the products
described perform correctly according
to their
descriptions. However, Research Machines Limited do
not accept liability for the consequences of any error or
omission.
Additional copies of
this publication may be ordered
from Research Machines Limited
at the address above.
Please
ask for the 'LINK 480Z Cassette System Users
Guide',
PN 11684.

Preface
The purpose of this manual is to enable you to install and start using the Research
Machines 480Z Cassette System.
It makes particular reference to the use of cassette
storage, BASICin ROM, and ROM packs. (If your480Z is equipped withdisc storage
and youwish to usedisc-based softwareyou sh9Uld refer to the manualsdeliveredwith
your 480Z disc drive, in particular
the "480Z Disc Systems Users Guide".)
Chapter 1of
this manual is ageneral introduction to microcomputers and the
terminology that you will need to become familiar with. Chapter 2is adescription of
the features and facilities of the 480Z cassette system. Chapter 3explains how to
install the 480Z cassette system and how to connect external devices, such as a
cassette recorder and avisual display unit.
When your
system is correctly installed you can begin using the BASIC language
interpreter,
as described in Chapter 4. Chapter 5describes the 480Z Resident
Operating
System (ROS) facilities and how to select the external devices, includinga
printer, for
input and output operations.
Appendix Aexplains hexadecimal notation, which you
may need to become familiar
with
as you read through this and the accompanying documentation.
Appendix Bis for more advanced users:
it gives details of 'escape sequences' that can
be used in BASIC
to make use of certain 480Z features for controlling the screen
display. Alist of useful escape sequences is provided
to assist you in writing your
BASIC programs.
Appendix Ccontains
the 480Z charactersets. The first is the normal set ofcharacters
available,
and the second is the graphics character set obtained when using the 480Z
in graphics mode.
Appendix Dprovides adetailed
"map" of the 480Z cassette system internal memory.
Appendix Eis aglossaryof some of
the terms used whendiscussing microcomputers.
Related Publications
This manual refers to the following publications, which are available from Research
Machines:
LINK 480Z BASIC IN ROM REFERENCE MANUAL, PN 11682
-This manual is essential for any user wishing to write BASIC programs for
execution under
the control of the 480Z BASIC in ROM interpreter.
ii

LINK 480Z INFORMATION FILE, PN 10939
-This manual contains detailed information about the LINK 480Z hardware,
especially
the physicalcharacteristicsof the input/output ports, the highresolution
graphics option,
and the printed circuit boards.
iii

CONTENTS
PAGE
CHAPTER 1INTRODUCTION TO MICROCOMPUTERS
What isaMicrocomputer
Hardware
Software
ProgrammingLanguages
Why'Micro'?
CHAPTER 2INTRODUCING
THE LINK
480Z CASSETTE SYSTEM
1.1
1.1
1.2
1.3
1.3
TheHardware
2.1
The480Z Keyboard 2.2
ControlKeys
2.3
TheSoftware 2.5
ROS, the
480Z0perating System 2.5
InternalMemoryof the 480ZCassetteSystem 2.6
CHAPTER 3INSTALLING THE 480Z CASSETTE SYSTEM
CheckingtheEquipment 3.1
Installation 3.2
Connecting
External Devices(Peripherals) to the 480Z 3.2
SwitchingOn
the System 3.4
ConnectionInformation 3.6
CHAPTER 4USING BASIC
ON THE
480Z CASSETTE SYSTEM
BASICinROM Interpreter 4.1
LoadingBASICProgramsfrom Cassette 4.2
Interrupting ProgramLoading 4.3
Errors inProgramLoading 4.3
SavingProgramsOnCassette 4.4
ROM Packs 4.5
PluggingintheROM Pack 4.6
Using
the ROM Packfor Machine-Code Programs 4.6
UsingtheROM Packfor BASICPrograms 4.6
RestartingBASICafter
an Error 4.7
EscapeSequences 4.8
iv

CHAPTER 5 ROS FACILITIES
ROSCommands 5.1
LoadingMachine-Code ProgramsfromCassette 5.2
Program
WRITER 5.2
ProgramTUNE 5.4
StoringMachine-Code ProgramsonCassette 5.5
SelectingaPrinterfor
the 480Z 5.6
TestingaPrinter 5.7
UsingaPrinterwitha'Ready' Line 5.8
ChangingCassetteSpeedOption 5.8
The480Z
Front Panel 5.9
SelectingaPrinterUsingthe
Front Panel 5.9
SwitchingtheScreenWidth 5.10
APPENDIX AHEXADECIMAL NOTATION
APPENDIX BESCAPE SEQUENCES
APPENDIX C
480Z DISPLAY CHARACTER SETS
APPENDIX D
480Z MEMORY USAGE MAP
APPENDIX EGLOSSARY OF TERMS
FIGURES
2.1
2.2
2.3
3.1
3.2
4.1
Basic480Z System
480Z Keyboard
480ZMemoryUsageMap
(64K)
480ZRearPanel
480ZMonitor
ROM Pack
v
2.1
2.2
2.6
3.6
3.6
4.6

INTRODUCTION TO MICROCOMPUTERS
Chapter 1
Introduction
to Microcomputers
This chapter introduces the basic concepts of microcomputer systems to users with
little or no previous knowledge of computer systems.
What is aMicrocomputer?
Amicrocomputer is an electronic machine which processes information rapidly. A
microcomputercannot
think for itself; it canonlydoexactly what it is instructed to do
by computer programs.
The term microcomputer
system generally refers to anumber of separate elements
which work together
to achieve arequired result. Theseelements can be thought ofin
two main groups;
the electronic machines, called hardware, and the computer
programs, called software.
Hardware
Atypical microcomputer system consists of:
• A keyboard
• A visual display
unit
• A processor
•
An internal memory
•
An external storage device
• A
printer
The keyboard lets you communicate with the processor.
The visual display
unit (VDU) lets you see what you have told the system to do, and
what messages the system has sent to you. These messages may include any other
information previously stored in
the computer system.
The processor,
as the name suggests, processes your information as instructed by a
computer program. The processor includes amicroprocessor
that executes programs
by performing arithmetical and logical operations on information stored in the
computer's memory.
This
memory is mainly 'volatile': volatile memory, usually called random access
memory(RAM), canbemodified
by aprogramduringprocessing, but when the system
is turned off the contentsofthismemoryarelost. Each time the system is turned on the
program and the information must be reloaded from a'non-volatile' storage device.
Theinternalmemoryalsoincludesread-onlymemory(ROM) whichis non- volatile;
the
contents of ROM are not lost when the system is turned off. This memory has special
uses within
the system.
1.1

INTRODUCTION TO MICROCOMPUTERS
The size of the memory available, whether volatile or non-volatile, is normally
expressed in terms ofKilobytes, where one byte comprises eight binary digits (bits) of
memory
and Kilo (K) represents the value 1024. One byte of memory can be used to
represent one character of information. For example, the 480Z is generally equipped
with 64K bytes of RAM, this means that the 480Z has 64 x1024 (= 65,536) bytes or
memory locations for storing programs and information.
The external storage media are usually aform of magnetic storage. Either magnetic
tape (cassettes) or magnetic discs are commonly used as storage media for
microcomputers.
These media hold the programs and items of data (files) that you will
be
using or creating. The processes involved are similar to those ofa tape recorder, as
described later.
Finally, you will
often need a printed copy of the results of the work performed by the
computer. This is provided by the printer. The copy is called alisting.
External input/output devices, such as VDUs, printers, and cassette recorders, are
usually referred to as peripheral devices.
Software
Software really means computer programs. Aprogram is asequence of instructions.
There
are two types of software:
•
System software
•Applications software
System software is a set of programs supplied by the computer system manufacturer.
Without these programs, it is an extremely laboriousprocess to write programs for the
system. The system software helps to make the computer easier to program and use.
The operating system is an example of system software. Another example is the
system software routines that are held permanently in the computer's non-volatile
(Read-Only) memory.
This type of software is frequently referred to as firmware.
Applications Software is a
set of programs which you may use to solve your specific
information
and data processing problems. These programs are designed to take care
of
the most commonly-used applications. This saves a lot of time for many users. For
example, this manual has been prepared using aword processing application program,
called WordStar*, that is available for use on many differentmicrocomputersysteqIs.
* WordStar is aregistered trademark of MicroPro. Inc.
1.2

INTRODUCTION TO MICROCOMPUTERS
Programming Languages
Both system and applications softwareobviouslyneed to bewritteninsomecomputer
language.
Many languagesarenow available but the most commonlyusedon the 480Z
is BASIC.
BASIC is called ahigh-level language because
it is easily written and understood by
computerusers, especially thosewithonly alittle knowledge ofcomputers. Therefore,
whenyou begin
to writeyourown applicationsprogramyouwill probablyuseBASIC.
Many applications programs provided
by Research Machines for your 480Z are
written in BASIC.
High-level languages need
to be translated into the machine code (binary digits) that
the computercanread and understand. Alanguagecompilerorinterpreterisprovided
for thispurpose,
and in the 480Z the BASI Cinterpreteris builtinto the machine, being
situated in ROM as firmware (hence, BASIC in ROM).
Assembly languagesarecalledlow-levellanguages because they are written inacoded
form (known
as mnemonic code) which is very like the internal machine code used by
the computer. Their advantage over high-level languages is that they arefaster to run
and more efficient in their use of the processor and memory. However, the task of
programmingin
an assembly language is much greater than in ahigh level language,
and consequentlyassemblylanguagesareusednormallyonly where considerationsof
execution speed
and memory space override those of programmer-productivity and
ease of program maintenance. Much system software and some applications software
is written in
an assembly language. The 'interpreter' for an assembly language is
known
as an assembler.
Why 'Micro'?
Computers vary according to their size, complexity, and cost. Microcomputer is the
name give to the smallest of the general purpose computers that are widely used in
industry, education, administration, and, increasingly,
the home. Microcomputers
possess
many of the features of the larger, more complex, and more expensive
computers. However, microcomputers areassembled in small cabinets
that areeasily
transported. They fit easily into
the existingoffice, laboratory, classroom, and home,
use asmall
amount of power, and cost substantially less than larger systems.
The
most significant differences between amicrocomputer and its larger cousins are
its much smaller capacity for storing information and, usually, alower speed for
processing
this information. In most other respects they provide the same facilities.
1.3

INTRODUCING THE LINK 480Z
Chapter 2
Introducing
the LINK
480Z Cassette System
In thischapter we shalllook at the 'make-up' ofthe480Z, beginningwith the hardware
andgoingon
to considertheoperatingsoftware and finally how the internalmemoryis
organized.
Before reading this chapter, remove
the equipment from its packing. You are shown
how to install the equipment in the
next chapter.
The Hardware
The Research Machines 480Z is built into amoulded structural foam case which
houses
the printed circuit boards, power supply, and the keyboard. AVDU (video
monitororadomestic television set)
and acassetterecorder areconnected to the480Z
tomakeupabasicsystem,
as showninFigure2.1. Other'peripheral' devices, such as a
printer or aROM pack, can be connected
as and when required.
Figure 2.1 Basic 480Z System
2.1

INTRODUCING THE LINK 480Z
Early 480Z machines were housed in ablack metal case. If you encounter this version,
don't worry; it functions identically to the later machine housed in the moulded
structural foam case. However, there are some important differences that you should
be aware of, and these are:
•Memory: A
number ofearly models were supplied with 32K bytes of random access
memory
•
BASIC in ROM: A number of early models were not fitted with BASIC in ROM
•80-Character Option: All machines
are now fitted with the 80-character option
allowing
the monitor text display as either 40-character lines or as 80-character
lines. Some earlier machines will only
permit a40-character line display
•
HRG: If your 480Z is fitted with the High Resolution Graphics (HRG) feature, it
will be possible to produce high resolution graphics output on the monitor.
Otherwise
you will be limited to low resolution graphics output. You can tellif your
480Z is equipped with this feature by checking the messages displayed when you
first start using BASIC in ROM (described in chapter 4)
If your 480Z has the HRG feature, you will also be able to produce colour graphics
output provided that you connect acolour monitor or colour TV able to process
TTL/RG Bsignals.
The 480Z Keyboard
Figure 2.2 shows the keyboard in closer detaiL
LlI\lK 480Z)
o
Figure 2.2 480Z Keyboard
2.2

INTRODUCING THE LINK 480Z
Thekeyboardholds two separate'blocks' ofkeys(or keypads), onelarge and onesmall.
The large keypad consists of alphabetic, numeric,
and symbol characters. Some keys
have only one character printed on
them but others have two, and this is explained
when
we look at the control keys in the next section.
Thelongkey
at the bottom ofthekeypadis calledthespace bar and is used to movethe
cursoracross
the VDU screen by entering 'space' characters The cursoris the square
that marks the position on the screen where any character you enter will appear.
The small keypad contains eight keys
(Fl, F2, F3, F4 and 'arrow' keys) which are
usuallyreferred to
as function keys. Thisis becausetheycanbeprogrammed by you to
perform particular functions, such as screen editing. The use of the function keys
depends on the application program you happen
to be running. Their functions are
different, for example, when programming in BASIC
to when using the text editing
facility, TXED. You canuse 'EscapeSequences'
to define what aparticularkey should
do,
and these are introduced in Chapter 4.
Keypad overlays are used to indicate the functions that each key will perform; these
are plastic overlays which slip easily over the eight keys. You should read the
appropriatemanualsfor
the softwarefor whichkeypadoverlaysareavailable(BASIC,
TXED, etc.)
to find out more about their use.
Control Keys
The use of the keyboard is demonstrated in chapter 4, but here we shall look at the
importantcontrolkeys and theway theyoperate. Thesekeysaredarkerincolour than
the otherkeys to make them easily identifiable. Whenyou have finished this chapter,
and have
set up your system as shown in chapter 3, you should come back to this
section
and practise using these keys:
ICAPS I
LOCK
The CONTROL key is used together with other keys to give
commands. Hold this key down while pressing
the key you require.
For example, pressing CTRL and F(you will see this written as
CTRL/F) puts the480Z Front PanelontotheVDUscreen.The Front
Panel is described in chapter 5(ROS facilities). You will be
introduced
to other control commands as you work through the
manual. Fulldescriptionsofallpossiblecontrolcommandsaregiven
in
the 480Z BASIC in ROM Reference Manual.
When pressed down
and 'locked' this causes all alphabetic
characters
to be displayed in upper case; otherwise they are
displayed in lower case.
2.3

INTRODUCING THE LINK 480Z
IRE:rURN I
ILINE I
FEED
This is the DELETE key and when pressed causes the character
immediately
to the left of the cursor to be deleted. The number of
charactersdeletedisequal
to the numberoftimes the keyispressed.
You will see this key mentioned many times throughout this
manual.
It is used when you enter commands and when you are
writing
and runningprograms. It is theway of telling the computer
that you haveenteredsomethingon the keyboard and younow want
it to obey acommand or store some information. When you see
IRETURN]written after acommand it means simply 'press the
RETURN key'.
Press akey
then press the REPEAT key. You will see that the
characteris repeateduntilyou release the
REPEAT key. If you hold
down the space bar and press I REPEAT Iyou will move the cursor
across
the screen.
Hold down this key
and press another key: if it is aletter key, the
letterwill be printedinuppercase(this is usefulifyou
don't want to
keep
the CAPS LOCK key down).
If it is adouble symbol key, the top symbol will be displayed.
It can also be used, in combination with other keys, for giving
commands
and thiswill be explained in the relevant part of the user
guide.
Pressingthis key moves thecursorverticallydown thescreen
to the
next line. It is usuallyonly usedwhen runningprograms and will be
explained in the relevant documentation for
the programs
concerned.
Like
the line feed function, the ESCAPE keyusuallyservesaspecial
function within programs
and will be explained in the relevant
documentation for the programs concerned.
We shall now look
at the software that controls all the activities of the 480Z.
2.4

INTRODUCING THE LINK 480Z
The Software
ROS, the 480Z Operating
System
The programs that make up the Resident Operating System, ROS, are permanently
stored in read-only memory
and are therefore termed 'firmware'. These (system)
programs are
not affected by any other (applications) programs you may run.
ROS controls
the internal operations of the computer and was designed to:
•Perform certain functions you request, from commands you
enter at the keyboard
•Control
the operation of the 'peripheral' devices connected to the 480Z, as well as
the keyboard
•Lookafter
the way the 64K bytes of480Zinternalmemoryareused by programsso
that you do not have to be concerned with what is happening inside the machine
•Allow you
to write and check low-level (machine code) programs
•Activate
the BASIC inROM interpreter(as describedlaterin the manual)whenyou
want to run BASIC
•Detect
the presence ofaROM packplugged into the back of the 480Z and take the
appropriate action, if required
ROS
starts up automatically when the 480Z is switched on or when the reset button
on the rear panel is pressed. The facilities that ROS provides are fully described in
chapter
5.
2.5

INTRODUCING THE LINK 480Z
Internal Memory of the 480Z Cassette Systems
FFFF (64K)
ROS
&workspace
1------------4 E800 (58K)
BASIC in ROM
1-----------1 9800 (38K)
USER
MEMORY
""'-- ~ 0000
Figure 2.3 480Z Cassette System Memory Usage
2.6
The 480Z is generally provided
with 64K
bytes of internal
memory. Figure 2.3 shows, in a
simplified form, how
this memory
is shared between
the various
system softwarecomponents such
as ROS and BASIC in ROM, as
well as the user programs.
User memory,
as the name
suggests, is
the random access
memory (RAM) available for you
to put data and programs into.
With the 480Z this is 58K; but if
you are running
BASIC in ROM,
the BASIC in ROM interpreter
prevents
the use of some of this
memory
and leaves you with up to
36K for your BASIC source
programs
and data.
The remaining 6K
bytes of
memory are reserved for ROS
and
includes some area to be used as
'workspace'.
If you want more details of the
memory map see Appendix C, or
refer
to the 480Z Information File.

INSTALLING THE 480Z
Chapter3
Installing the 480Z Cassette System
This chapter explains how to install the 480Z and how to connect the VDU and the
cassette recorder.
Checking the Equipment
When you unpack the 480Z, check that you have received:
•The 480Z microcomputer
• A
cassette containing some demonstration programs
• A
cassette containing the TXED (Text Editor) program, if ordered
• A connecting lead for a
UHF television
Other equipment and their accessories may also be included according to your
requirements. However,
to operate your 480Z you will need at least the following:
• A VDU for black
and white (monochrome) display and which can be either:
- a
UHF television (either colour or monochrome)
- a monochrome character display monitor
• A
cassette recorder (and its mains lead) and aconnecting lead
• A 3-way
or 4-way mains adaptor
• 3-pin plugs to connect the above items to the mains supply.
If your 480Z is fitted with the High Resolution Graphics (HRG) feature, it is also
capable ofgeneratingcolour displays
through the socketmarked TTL/RGB. For this
you will need acolour monitor (or acolour television) with the TTL/RGB capability.
More
than one type of VDUcan be connected simultaneously to a480Z, Le. UHF TV,
monochrome monitor,
and TTL/RGB monitor. All will produce the same display.
The mains lead on
the monitor supplied by Research Machines may already have a
continental
plug moulded to it. Please cut this plug off and attach a standard plug,
3.1

INSTALLING THE 480Z
taking all safety precautions.
Please keep all
the boxes and packing, ifpossible. In the event of the equipment being
transported for any reason, this packing will help prevent damage to it.
Installation
Whenyouinstallyour480Z, you shouldplace it onaconvenientwork surfaceclose to a
mains poweroutlet. A
suggested layout is to place the keyboardinfront of the display
unit.
Other itemsofequipment, such as cassette recorder or aprinter, shouldbeplaced
as close as possible to the 480Z to enable you(or the operator) to be able to reach them
easily. Do not forget to provide enough work surface for papers and manuals.
The 480Z
and its accessories should not beexposed to direct sunlight. Theventilation
slitson
the rearpanelshould not beobstructed;also, the socketson the rear panelof the
480Z shouldremainaccessibleifyou intend to connect and disconnectexternaldevices
from time
to time without disturbance.
Connecting External Devices (Peripherals) to the 480Z
In abasic system (sometimes called abasic configuration) the peripherals include a
VDU
and cassette recorder, as mentioned earlier. A printer may also be added when
needed. Before connecting
them to your 480Z, note these important points:
•All
the equipmentshouldbe connected to the samemains adaptor orextensionlead
•The mains supply
to the adaptor or extension lead must be switched off
•You should refer
to the diagrams of the 480Z rear panel and monitor for guidance.
These diagrams are shown in figures 3.1
and 3.2
Visual Display Unit
This can be amonochrome or colour monitor, or adomestic television set. The
connections to
the 480Z are different for each.
Instructions for installing the Panasonic monochrome monitor are provided in the
Installation Notes for the Panasonic Monitor(PN 11293), which are included with the
monitor. Aseparate cable is also provided.
•Connect one end of
the cable to the VIDEO IN socket at the rear of the monitor
3.2