Radio Shack TRS-80 Model 3 User manual

TRS·BO™
Model III
•
peratlon
and ASI
Langua e
Refer nee
nu I
Itadle Ihaek ®
MA DIVISION OF TANDY CORPORATION
FORT WORTH, TEXAS 76102

TRS·80 Model HI Operation and BASIC
Language Reference Manual: ©1980 Tandy
Corporation, Fort Worth, Texas 76102 U.S.A.
All Rights Reserved.
Reproduction or use, without express written
permission from Tandy
Corporation. of any
portion
of this manual is prohibited. While
reasonable efforts have been taken in the
preparation
of this manual to assure its accuracy.
Tandy Corporation assumes
no liability resulting
from any errors or omissions
in this manual. or
from the use
of the information obtained herein.
Model III System Software: ©1980 Tandy
Corporation and Microsoft. All Rights
Reserved.
The system software in the Model III
microcomputer
is retained in aread-only memory
(ROM) format. All portions of this system
software. whether in the ROM format or other
source code form format, and the
ROM circuitry,
are copyrighted and are the proprietary and trade
secret information
of Tandy Corporation and
Microsoft. Use. reproduction or publication
of any
portion
of this material without the prior written
authorization
by Tandy Corporation is strictly
prohibited.
10 9 8 7 6 5 4 3 2

To OurCustomers. •
The TRS-80@ Model III COITlputer is avery powerful tool for business, home and
recreation. Twenty years ago, this capability would have costhundreds
of times as
much as yourModel III cost, and wouldhave taken up an entire room.
In spite
of its power and internal complexity, the Model III canbe quite simple to
operate. In fact, you candetermine
just how' 'technical" amachine you want it to
be.
At the simplestlevel of operation, you can use RadioShack prepared cassette
programs. All
you will needto know is how to load and run acassette program, and
howto operate the cassette recorder.
If this is where you wantto start, read
Chapters 1through 6
of the Operation Section. You may also want to read about
CLOAD and SYSTEM in Chapter2 of the Language Section.
If you wantto writeyourown programs and you are abeginner, read Chapters 1
through6
of the OperationSection, then startreadingthe book, Getting Started
with TRS-80 BASIC. That, plus severalotherRadio Shackbooks, canguideyou to
becomingaprogrammerin BASIC and Z-80 language (' 'machine code'').
If you already know BASIC, and especially if youhaveexperience on aTRS-80
Model I, read the entireOperation Section of this manual, as well as the Appendix
whichcompares the Model Iand Model III. The Model III has many unique
features andsome very importantdifferences. Afew minutes spentbefore you
press
(ENTER) couldsave you hours later.
About Manual
This manual contains operating instructions (Section 1) and adescription of Model
III BASIC (Section 2and Appendix). It is arranged for easy reference, whether you
are seeking simple
or technical information. Page numbering starts overat the
beginning
of eachchapter, and chapternumbering starts overat the beginning of
eachsection. There is acomprehensive Index at the end of this book.
If you are abeginner, don't worry aboutthe technical parts in the Operation
Section.
The beginning of eachchapteris for you. (When you getto the POKE
statements, youcan skip ahead to the next chapter ... )You don't needto read past
Chapter6.
Then, when you learn simple BASIC programming, you can return and
try
out all the' 'goodies" packedintoyourModel III.

TRS-SO MODEL III
C nt nts
Operation Section
ABrief Description of the Computer 1/1-3
Installation 2/1-3
Operation 3/1-9
Power-On DRESET Switch DPower-Off DStart-Up Dialog
DModes of Operation DSample Session
Using the Keyboard 4/1-3
Capitals and Lowercase DSpecial Keys DControl Codes
Using the Video Display 5/1-5
Character Size Cursor DScroll Protection DText D
Graphics DSpace Compression DSpecial Characters
Using the Cassette Interface 6/1-6
Cassette TransferSpeed DLoading Errors DSaving aBASIC
Program on Tape DLoading aBASIC Program from Tape D
How to Search for aProgram DLoading aSYSTEM Tape D
Searching for aProgram
Using aLine Printer 7/1-6
Line Printer vs Video Display Output 0Printer Control
Features DPrint Screen Function
Using the RS .. 232 .. CInterface 8/1-8
What is an Interface? DUsing the Model III as aTerminal 0
Programming the RS-232-C
Routing Input/Output 9/1-3
To Route from One Device to Another DRouting Multiple
Devices
Real .. Time Clock. ................................... .. 10/1-3
To Set the Clock 0To Read the Clock DTo Display the Clock
Input/Output Initialization 11/1-1
Technical Information ............................. .. 12/1-26
To Protect High RAM DROM Subroutines Memory Map
oSummary of Important ROM Addresses Summary of
Important RAM Addresses
Troubleshooting and Maintenance 13/1-3
Symptom/Cure Table DAC Power Sources 0Maintenance
Specifications. . . . . .. . .. . . . .. . .. . . .... . . .. .. . .. .. . .. .. 14/1-3
Power Supply DMicroprocessor 0RS-232-C Interface
DParallel (Printer) Interface Cassette Interface
ii

BASIC Language Section
BASIC Concepts 1/1-30
Commands 2/1-7
Input-Output Statements 3/1-13
Program Statements 4/1-15
Strings '5/1-9
Arrays 6/1-6
Arithmetic Functions 7/1-5
Special Features 8/1-10
Editing 9/1-7
Appendices
Model III Summary A/1-18
Special Charactersand Abbreviations 0Commands 0State-
ments0Functions Reserved Words 0Program Limits
MemoryUse0Accuracy 0
Error Codes B/1-3
TRS-SO Model III Character Codes C/1-9
Keyboard/DisplayCharacters Graphics0Special Charac-
ters 0Video DisplayWorksheet0
Internal Codes for BASIC Keywords 0/1-2
Derived Functions E/1-2
Base Conversions F/1-4
Model I
to Model III Program Conversion Hints G/1-2
Glossary H/1-3
RS-232-C Technical Information
1/1-4
Index
ForWarrantyand CustomerInformation,seethebackcoverand
insidebackcover.
iii

1/ ABriefDescription
The Radio Shack TRS-80@ Model III is aROM-based computersystemconsisting of:
.. A12-inch screen to display results and otherinformation
• A 65-key consolekeyboard for inputting programs and data to the Computer
.. A Z-80 Microprocessor, the" brains" of the system
• A Real-TimeClock
•ReadOnly Memory (ROM) containingthe Model III BASIC Language (fully
compatible with mostModel I
BASIC programs)
•Random Access Memory (RAM) for ?torage of programs and data while the
Computeris on (amount is expandable from
"16K" to "48K", optional extra)
• A CassetteInterfacefor long-termstorage of programs and data (requires a
separatecassette recorder, optional/extra)
• A PrinterInterfacefor hard-copy output of programs and data (requires a
separate line printer, optional/extra)
•Expansion area for upgrading to adisk-basedsystem (optional/extra)
•Expansionareafor an RS-232-C serial communications interface (optional/extra)
All thesecomponents are contained in asingle molded case, and all are powered via
one
power cord.
VideoDisplayScreen
Displayablecharacters include the standard 96 text-characters with the upper and
lowercase alphabet;
64 graphics characters; and 160 special TRS-80 characters. In
addition, there are numerous control and space-compression characters. Some
of
thecharactersets can be switchedin and outby BASIC andotherprograms.
Keyboard
The keyboard allows entry of all the standard text and control characters. It also
includes a12-key section forconvenient numeric entry. From the keyboard, you
canselecteitherall-capitals
or upperand lowercaseentry. The (BREAK) key is
designed to return control to you during any operation, including cassette
input/output
or line printeroutput. Every key has an auto-repeat feature.
1/1

TRS-SO MODEL III
Z-80Microprocessor
This is the central processing unit-where all the' 'thinking" is done. In the Model
III, the microprocessoroperates at aspeed
of over two million cycles persecond.
Read OnlyMemory(ROM)
This is where the Computer's built-in programs are stored, including the TRS-80
BASIC language. TRS-80 BASIC is fully compatible with the Level II language used in
Model I
TRS-80' s. Each time you power-on the Computer, this ROM program takes
charge
of the microprocessor, enabling you to type in simple BASIC-language
instructions.
The Model III contains a"14K" ROM, meaning it contains 14 * 1024 = 14336
characters (' 'bytes' ') of permanently programmed memory.
Random Access Memory(RAM)
This is where yourprograms and results are stored while the Computeris on. It is
erasedwhen you turn the Computeroff.
The Model III can be equipped with 16K, 32K or 48K of RAM ( IK=1024 bytes).
Peripherals
These are devices you canadd to yourCoruputerto increase its usefulness in
programmingand data storage.
The Model III contains the necessary" interfaces',
to simplifythe addition
of many peripherals.
Cassette
For long-term storage of programs anddata, simply connect acassette recorder to
the Computer, and save the information
on tape.
For programstorage, you rnay selecteitherHigh or Low transferrates (use Low for
compatibility with
Model I, Highfor faster saves and loads).
1/2

Printer
You may connectany Radio Shack' 'parallel interface" printerto the Model III;
this will give you "hard-copy" capability for program listings, reports, mailing
lists, invoices, etc.
Other Enhancements
The Model III contains spacefor amini-disk controller and one or two mini-disk
drive units.
The Computerwill accommodate one ortwoexternal drive units as
well.
With aone-, two-, three-
or four-drive system, you will be able to store and retrieve
programs and data bothquickly and reliably. YourComputerwill then be under the
control
OfTRSDOS@, the powerful Radio Shack DiskOperating System.
Youcan also add an internal
RS-232-C serial interface. This will allow your
computerto communicate with an
RS-232-C equipped computer, serial line printer
or other serial device.
1/3

2/Installation
Carefullyunpackthe Computer. Remove all packing material and save itin case
you
ever needto transportthe Computer. Besureto locate all cables, papers, etc. ,
thatmaybe includedinthe shippingcarton.
Placethe Computer
on the surface where you'll be using it. An appropriate power
sourceshouldbe nearby, so thatno extensioncordwill be required.
Donotconnectthe Computertothe AC powersource yet.
Connection of Peripherals
Beforeconnecting any peripherals (forexample, line printerand cassette recorder),
makesure the Computerand theperipheral devices are turned off.
Connectall peripherals to the appropriatejacks on the bottom and rear
of the
Computer. Referto Figure 1for location
of connectionpoints. For interconnections
betweencables andperipherals, referto the
Owner's Manual supplied with the
peripheral device.
Note: All cables shouldexit to the rear
of the unit so that no binding occurs.
2/1

TRS-80 MODEL III
On/Off Switch
Disk Expansion Jack. Shown with cable
connected. Cable is supplied with external
drives (optional/extra).
Parallel PrinterJack. Shown with cable con-
nected. Cable and printer are optional/extra.
RS-232-C Jack. Shown with cable
connected. Cable and RS-232-C Interface
are optional/extra.
eI/O Bus Jack. For future expansion.
Cassette Jack. Shown with cable con-
nected. Cable and cassette recorder are
optional/extra. Black mini-plug connects
to
recorder EAR; gray mini-plug to recorder
AUX; graysUbmini-plug to MIC REMote con-
trol.
G AC Power Cord.
eVideo Contrast Adjustment.
oVideo Brightness Adjustment.
Figure1. Connection of peripherals and locationofcontrols.
2/2

Connection of aCassette Recorder
The following instructions use the CTR-80A recorder(Radio ShackCatalog Number
26-1206) as an example. If you use adifferentrecorder, connection and operation
may vary.
Note: You do notneedto connectthe CassetteRecorderunless you plan to record
programs
or to loadtaped programs into the TRS-80.
A TRS-80 to Cassette Recorderconnection cable is included with the CTR,80A; we
suggestthatyou use this speciallydesigned cable.
1. Connect the shortcable (DIN plug on one end and three plugs on the other) to the
T APE jack on the back of the Computer. Be sure you getthe plugto mate
correctly.
2.
The three plugs on the otherend of this cable are for connectingto the recorder.
3. A.
Connect the blackplug into the EARjack on the side ofthe recorder. This
connectionprovides the output signal from the recorderto
TRS-80 (for
loading
Tape programs into TRS-80).
B. Connect the larger gray pluginto the Auxjack on the recorder. This
connectionprovides the recording signal to record programs from the
TRS-80 onto the tape.
Leave the AUX pluginwhetheryou are recording or playing back
cassette data.
C. Connect the smallergray plug into the smaller MIC jack on the recorder.
This allows the
TRS-80 toautomatically control the recordermotor (turn
tape motion
on and off for recording andplaying tapes.)
Note: Do notplug aremote microphone or a dummy plug into the larger MIC jack.
Connectionto an AC PowerSource
Make surethe Computer and all peripherals are off.
The AC Power Cord exitsfrom the rear of the Computer. Connectitand all
peripheralsto an appropriate
power source. Power requirements for Radio Shack
products are specified
on the units andinthe Owner's Manual Specifications.
For convenience, you may connectall components to a single' 'power strip" such
as
Radio Shack's 26-1451 Line Filter. This will allow you to turn on the entire system
with asingle switch.
Take carenotto exceedthecurrentcapacity of the power strip.
2/3

3/Operation
Power-On
Thefollowing instructions explainhow to start up and use the Model III as a
ROM-based
system only.
If youhave aDiskSystemand are going to loadTRSDOS, follow the power-up
instructions given inthe Model III Disk System
Owner's Manual. If youhave a
DiskSystem
but you are notgoing to load TRSDOS, read the instructions laterin this
chapter.
TheComputerandall peripherals mustbe off.
First turn on all peripherals, then turn on the Computer.
(If you have all the
components connected to apowerstrip, justturn on the power strip.)
Afterafew seconds, the following message should appearonthe Video Display:
Cass?
Themeaning of this message will be explained later.
If the messagedoes not appear:
A. TheVideo Display may need Brightness orContrastadjustment. See Figure 1
for location
of these controls.
B.
If the message still doesn't appear, thenturn off the entire system;recheck all
connections, andtry again. Forfurther assistance,
see' 'Troubleshooting and
Maintenance.' ,
Donotturn any peripherals
off while the Computeris inuse; to do so could cause
abnormal operation (the Computercouldrestart
or' 'hang up" ,requiring you to
resetorturn the system
off and on again).
3/1

TRS-80 MODEL III
RESET
RESET is the orange-colored button at the upper right corner of the keyboard.
To' 'startover" at the power-onmessage, you do not have to tum the unit off and
on again. Pressing the
RESET button will have the same effect.
Note: Resetting the Computerdoes not erase the contents of RAM. However, the
BASIC languageinterpreterwill start over, thus' 'losing" any programordata you
had in memory.
Tointerrupt aprogram
or operation without losing yourBASIC program and data,
hold down the
(BREAK) key.
Power-Off
First tum off the Computer, then all otherperipherals.
If you tum the Computer off for any reason, leave it off for at least 15 seconds before
turning it back
on again. TheComputer's powersupply needs this time to discharge
its storedenergybeforestarting up again.
Wheneveryou
tum off the Computer, all programs and data are erased. So be sure
to save yourinformation (e.g. ,on cassette) before turning
off the Computer.
Start-UpDialog
Whenyou tum on or resetthe Computer, it asks you two questions. First:
Cass?
This question lets you determine the rate at whichprograms and data will be
transferred to andfrom cassette. You can select eitherLow (500 baud) orHigh (1500
baud). Type
L
forLow, or
H
for High.
3/2