Rockwell Automation Allen-Bradley SLC 500 BASIC User manual

BASIC Language
(Catalog Numbers 1746-BAS and
1746-BAS-T)
Reference Manual

Important User
Information
Because of the variety of uses for the products described in this publication, those
responsible for the application and use of this control equipment must satisfy
themselves that all necessary steps have been taken to assure that each application
and use meets all performance and safety requirements, including any applicable
laws, regulations, codes and standards.
The illustrations, charts, sample programs and layout examples shown in this
guide are intended solely for purposes of example. Since there are many variables
and requirements associated with any particular installation, Rockwell
International Corporation does not assume responsibility or liability (to include
intellectual property liability) for actual use based upon the examples shown in
this publication.
Rockwell Automation publication SGI-1.1, Safety Guidelines for the Application,
Installation and Maintenance of Solid-State Control (available from your local
Rockwell Automation office), describes some important differences between
solid-state equipment and electromechanical devices that should be taken into
consideration when applying products such as those described in this publication.
Reproduction of the contents of this copyrighted publication, in whole or part,
without written permission of Rockwell Automation, is prohibited.
Throughout this manual we use notes to make you aware of safety considerations:
Attention statements help you to:
•identify a hazard
•avoid a hazard
•recognize the consequences
PLC-5 is a registered trademark; and MicroLogix, SLC 500, RSLogix, and RSLinx are trademarks of Rockwell Automation.
ATTENTION

Identifies information about practices or circumstances that
can lead to personal injury or death, property damage or
economic loss
IMPORTANT Identifies information that is critical for successful
application and understanding of the product.

iPublication 1746-RM001A-US-P
Table of Contents
Preface
Who Should Use This Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P-1
Purpose of this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P-2
How to Use this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P-3
Terms and Abbreviations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P-4
Conventions Used in this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . P-4
Rockwell Automation Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . P-5
Chapter 1
Language Elements
Character Set. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
The BASIC Program Line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
Chapter 2
Data Types
Data Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
Chapter 3
Expressions and Operators
Expressions and Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
Hierarchy of Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
Arithmetic Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
Logical Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
Relational Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7
Trigonometric Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8
Functional Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9
Logarithmic Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11
String Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-12
Special Function Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15
Chapter 4
BASIC Commands
BRKPNT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
CONT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
Control-C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4
CALL 18 – Re-enable the Control-C Break Function . . . . . . . . . . . . . 4-5
CALL 19 – Disable the Control-C Break Function . . . . . . . . . . . . . . . 4-6
Control-S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7
Control-Q. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
EDIT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
ERASE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9
IDLE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10
LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-11
LIST@ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
LIST# . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12
NEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14

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NULL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-14
PROG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-15
PROG1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-16
PROG2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17
RAM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-19
REM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-19
REN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-20
ROM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-20
RROM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-21
RUN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-22
SNGLSTP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-23
VER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-25
XFER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-26
Chapter 5
Command Line CALLs
CALL 73 – Battery-Backed RAM Disable. . . . . . . . . . . . . . . . . . . . . . 5-1
CALL 74 – Battery-Backed RAM Enable . . . . . . . . . . . . . . . . . . . . . . 5-2
CALL 77 – Protected Variable Storage . . . . . . . . . . . . . . . . . . . . . . . . 5-2
CALL 81 – User Memory Module Check and Description. . . . . . . . . 5-3
CALL 82 – Check User Memory Module Map. . . . . . . . . . . . . . . . . . 5-4
CALL 101 – Upload User Memory Module Code to Host. . . . . . . . . 5-4
CALL 103 – Print PRT1 Output Buffer and Pointer . . . . . . . . . . . . . 5-5
CALL 104 – Print PRT1 Input Buffer and Pointer. . . . . . . . . . . . . . . 5-6
CALL 109 – Print Argument Stack. . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7
CALL 110 – Print PRT2 Output Buffer Pointer . . . . . . . . . . . . . . . . 5-8
CALL 111 – Print PRT2 Input Buffer Pointer . . . . . . . . . . . . . . . . . . 5-8
Chapter 6
Assignment Functions
CLEAR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1
CLEARI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
CLEARS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
DATA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4
DIM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4
LET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5
RESTORE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7
Chapter 7
Control Functions
CLOCK1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1
CLOCK0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2
DO-WHILE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3
DO-UNTIL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4
END. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-5
FOR-TO-(STEP)-NEXT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6
GOTO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7
IF-THEN-ELSE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-8

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NEXT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-9
ON-GOTO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-11
Chapter 8
Execution Control and
Interrupt Support Functions
CALL 16 – Enable DF1 Packet Interrupt . . . . . . . . . . . . . . . . . . . . . . 8-2
CALL 17 – Disable DF1 Packet Interrupt. . . . . . . . . . . . . . . . . . . . . . 8-3
CALL 20 – Enable Processor Interrupt . . . . . . . . . . . . . . . . . . . . . . . . 8-3
CALL 21 – Disable Processor Interrupt. . . . . . . . . . . . . . . . . . . . . . . . 8-4
CALL 26 – Module Interrupt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4
CALL 38 – Expanded ONERR Restart. . . . . . . . . . . . . . . . . . . . . . . . 8-5
CALL 70 – ROM to RAM Program Transfer . . . . . . . . . . . . . . . . . . . 8-8
CALL 71 – ROM/RAM to ROM Program Transfer. . . . . . . . . . . . . . 8-9
CALL 72 – RAM/ROM Return . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-9
GOSUB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-11
ONERR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-12
ON-GOSUB. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-14
ONTIME . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-14
PUSH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-15
POP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-17
RETI. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-18
RETURN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-18
STOP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-20
Chapter 9
Math and Backplane
Conversion Functions
CALL 14 – 16-Bit Signed Integer to BASIC Floating-Point . . . . . . . . 9-1
CALL 15 – 16-Bit Unsigned Integer to BASIC Floating-Point. . . . . . 9-2
CALL 24 – BASIC Floating-Point to 16-Bit Signed Integer . . . . . . . . 9-2
CALL 25 – BASIC Floating-Point to 16-Bit Binary . . . . . . . . . . . . . . 9-3
CALL 88: BASIC Floating-Point to SLC Floating-Point. . . . . . . . . . . 9-4
CALL 89: SLC Floating-Point to BASIC Floating-Point. . . . . . . . . . . 9-5
Chapter 10
Clock/Calendar Functions
CALL 40 – Set Clock/Calendar Time . . . . . . . . . . . . . . . . . . . . . . . . 10-1
CALL 41 – Set Clock/Calendar Date . . . . . . . . . . . . . . . . . . . . . . . . 10-2
CALL 42 – Set Day of Week. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-3
CALL 43 – Retrieve Date/Time String . . . . . . . . . . . . . . . . . . . . . . . 10-4
CALL 44 – Retrieve Date Numeric. . . . . . . . . . . . . . . . . . . . . . . . . . 10-4
CALL 45 – Retrieve Time String . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-5
CALL 46 – Retrieve Time Numeric . . . . . . . . . . . . . . . . . . . . . . . . . 10-6
CALL 47 – Retrieve Day of Week String . . . . . . . . . . . . . . . . . . . . . 10-6
CALL 48 – Retrieve Day of Week Numeric . . . . . . . . . . . . . . . . . . . 10-7
CALL 52 – Retrieve Date String . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-7

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Chapter 11
Status Functions
CALL 36 – Get Number of Characters in PRT2 Buffers . . . . . . . . . 11-2
CALL 51 – Check CPU Output Image Buffer . . . . . . . . . . . . . . . . . 11-3
CALL 55 – Check CPU Input Image Buffer. . . . . . . . . . . . . . . . . . . 11-4
CALL 58 – Check M0 File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-5
CALL 59 – Check M1 File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-6
CALL 75 – Check SLC 500 Controller CPU Status . . . . . . . . . . . . . 11-7
CALL 80 – Check Battery Condition . . . . . . . . . . . . . . . . . . . . . . . . 11-8
CALL 86 – Check DH485 Interface File Remote Write Status. . . . . 11-8
CALL 87 – Check DH485 Interface File Remote Read Status . . . . . 11-9
CALL 95 – Get Number of Characters in PRT1 Buffers . . . . . . . . 11-10
CALL 97 – Enable Port PRT2 DTR Signal . . . . . . . . . . . . . . . . . . 11-11
CALL 98 – Disable Port PRT2 DTR Signal. . . . . . . . . . . . . . . . . . 11-11
CALL 108 – Enable DF1 Driver Communications. . . . . . . . . . . . . 11-12
CALL 113 – Disable DF1 Driver Communications . . . . . . . . . . . . 11-18
CALL 120 – Clear module Input and Output Buffers . . . . . . . . . . 11-18
CALL 121 – Get SLC Processor Program ID Number . . . . . . . . . . 11-19
Chapter 12
Output Functions
CALL 23 – Transfer Data from the CPU Files to Port 1 or 2 . . . . . . 12-2
CALL 28 – Write to Remote DH485 SLC Data File . . . . . . . . . . . . 12-6
CALL 29 – Read/Write to a PLC/SLC from the
Module Internal String . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-13
CALL 31 – Display Current PRT2 Port Setup . . . . . . . . . . . . . . . . 12-14
CALL 37 – Clear PRT2 Input/Output Buffers . . . . . . . . . . . . . . . . 12-15
CALL 54 – Transfer BASIC Output Buffer to CPU Input Image. . 12-15
CALL 57 – Transfer BASIC Output Buffer to CPU M1 File . . . . . 12-16
CALL 85 – Transfer BASIC Output Buffer to DH485
Common Interface File. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-17
CALL 91 – Write BASIC Output Buffer to Remote DH485 Data File 12-18
CALL 93 – Write Output Buffer to Remote DH485
Common Interface File. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-22
CALL 94 – Display Current PRT1 Port Setup . . . . . . . . . . . . . . . . 12-24
CALL 96 – Clear PRT1 Input/Output Buffers . . . . . . . . . . . . . . . . 12-24
CALL 112 – User LED Control . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-25
CALL 114 – Transmit DF1 Packet. . . . . . . . . . . . . . . . . . . . . . . . . 12-26
CALL 115 – Check DF1 XMIT Status. . . . . . . . . . . . . . . . . . . . . . 12-27
CALL 123 – Write to Remote DF1 PLC Data File. . . . . . . . . . . . . 12-28
PRINT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-35
PH0., PH1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-37
ST@ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-38

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Chapter 13
Input Functions
CALL 22 – Transfer Data from Port 1 or 2 to the CPU Files . . . . . . 13-2
CALL 27 – Read Remote DH485 SLC Data File . . . . . . . . . . . . . . . 13-8
CALL 29 – Read/Write to a PLC/SLC from the
Module Internal String . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-13
CALL 35 – Get Numeric Input Character from PRT2 . . . . . . . . . . 13-15
CALL 53 – Transfer CPU Output Image to BASIC Input Buffer. . 13-17
CALL 56 – Transfer CPU M0 File to BASIC Input Buffer. . . . . . . 13-18
CALL 84 – Transfer DH485 Interface File to BASIC Input Buffer. 13-19
CALL 90 – Read Remote DH485 Data File to BASIC Input Buffer 13-20
CALL 92 – Read Remote DH485 Common Interface File to
BASIC Input Buffer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-23
CALL 117 – Get DF1 Packet Length . . . . . . . . . . . . . . . . . . . . . . . 13-25
CALL 118 – PLC/SLC Unsolicited Writes . . . . . . . . . . . . . . . . . . . 13-26
CALL 122 – Read Remote DF1 PLC Data File . . . . . . . . . . . . . . . 13-30
GET . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-38
INPL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-39
INPS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-40
INPUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-40
LD@ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-43
READ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-45
Chapter 14
Setup Functions
CALL 30 – Set PRT2 Port Parameters . . . . . . . . . . . . . . . . . . . . . . . 14-1
CALL 78 – Set Program Port Baud Rate. . . . . . . . . . . . . . . . . . . . . . 14-2
CALL 99 – Reset Print Head Pointer . . . . . . . . . . . . . . . . . . . . . . . . 14-3
CALL 105 – Reset PRT1 to Default Settings . . . . . . . . . . . . . . . . . . 14-4
CALL 119 – Reset PRT2 to Default Settings . . . . . . . . . . . . . . . . . . 14-4
MODE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-5
Chapter 15
String Functions
CALL 60 – String Repeat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1
CALL 61 – String Append . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-2
CALL 62 – Number to String Conversion . . . . . . . . . . . . . . . . . . . . 15-3
CALL 63 – String to Number Conversion . . . . . . . . . . . . . . . . . . . . 15-4
CALL 64 – Find a String in a String . . . . . . . . . . . . . . . . . . . . . . . . . 15-6
CALL 65 – Replace a String in a String. . . . . . . . . . . . . . . . . . . . . . . 15-7
CALL 66 – Insert a String in a String . . . . . . . . . . . . . . . . . . . . . . . . 15-8
CALL 67 – Delete a String in a String. . . . . . . . . . . . . . . . . . . . . . . . 15-9
CALL 68 – Find the Length of a String. . . . . . . . . . . . . . . . . . . . . . 15-10
STRING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-11

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Table of Contents vi
Appendix A
Decimal/Hexadecimal/Octal/
ASCII
Conversion Table
Mathematical Conversion Overview . . . . . . . . . . . . . . . . . . . . . . . . . . A-1
Appendix B
BASIC Command, Statement,
and CALL Quick Reference
Guide
Mnemonic List Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1
Index

P-1 Publication 1746-RM001A-US-P
Preface
Read this preface to familiarize yourself with the rest of the manual. This preface
covers the following topics:
•who should use this manual
•the purpose of this manual
•how to use this manual
•terms and abbreviations
•conventions used in this manual
•Rockwell Automation support
Who Should Use This
Manual
Use this manual if you are responsible for designing, installing, programming, or
troubleshooting control systems that use Allen-Bradley small logic controllers.
You should have a basic understanding of SLC 500™ products. You should
understand programmable controllers and be able to interpret the ladder logic
instructions required to control your application. If you do not, contact your local
Rockwell Automation representative for information on available training courses
before using this product.

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Purpose of this Manual
This manual is a reference guide for programming the BASIC or BASIC-T
module. This manual is intended for reference purposes only.
Chapter Title Contents
Preface Describes the purpose, background, and scope of this manual. Also lists related
publications.
1 Language Elements Describes BASIC program lines, line numbers, statements, commands,
operators, and line length.
2 Data Types Describes and illustrates data types, variable names and types.
3 Expressions and Operators Describes and illustrates arithmetic, logical, relational, trigonometric, functional,
logarithmic, string, and special function operators.
4 BASIC Commands Describes and illustrates BRKPNT, CONT, [CTRL-C], [CTRL-S], [CTRL-Q], EDIT,
ERASE, IDLE, LIST, LIST@, LIST#, MODE, NEW, NULL, PROG, PROG1, PROG2,
RAM, REM, REN, ROM, RROM, RUN, SNGLSTP, VER, and XFER commands and
CALLs 18 and 19.
5 Command Line CALLS Describes and illustrates CALLs 73, 74, 77, 81, 82, 101, 103, 104, 109, 110, and
111.
6 Assignment Functions Describes and illustrates CLEAR, CLEARI, CLEARS, DATA, DIM, LET and
RESTORE functions.
7 Control Functions Describes and illustrates CLOCK1, CLOCK0, DO-WHILE, DO-UNTIL, END,
FOR-TO-(STEP)-NEXT, GOTO, IF-THEN-ELSE, NEXT, and ON-GOTO functions.
8 Execution Control and Interrupt
Support Functions
Describes and illustrates CALLs 16, 17, 20, 21, 26, 38, 70, 71, 72, and GOSUB,
ONERR, ON-GOSUB, ONTIME, PUSH, POP, RETI, RETURN, and STOP functions.
9 Math and Backplane Functions Describes and illustrates CALLs 14, 15, 24, 25, 88, and 89.
10 Clock/Calendar Functions Describes and illustrates CALLs 40, 41, 42, 43, 44, 45, 46, 47, 48, and 52.
11 Status Functions Describes and illustrates CALLs 36, 51, 55, 58, 59, 75, 80, 86, 87, 95, 97, 98, 108,
113, 120, and 121.
12 Output Functions Describes and illustrates CALLs 23, 28, 29, 31, 37, 54, 57, 85, 91, 93, 94, 96, 112,
114, 115, 123, and PRINT, PH0. PH1. and ST@ functions.
13 Input Functions Describes and illustrates CALLs 22, 27, 29, 35, 53, 56, 84, 90, 92, 117, 118, 122,
and GET, INPL, INPS, INPUT, LD@ and READ functions.
14 Setup Functions Describes and illustrates CALLs 30, 78, 99, 105, 119, and MODE functions.
15 String Functions Describes and illustrates CALLs 60, 61, 62, 63, 64, 65, 66, 67, 68, and STRING
functions.
Appendix A Decimal/Hexidecimal/Octal/
ASCII Conversion Table
Lists the Decimal/Hexidecimal/Octal/ASCII equivalents.
Appendix B BASIC Command, Statement, and
CALL Quick Reference Guide
Lists the various commands, statements, and CALLs needed for BASIC
programming.

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Related Documentation
The following documents contain additional information regarding Rockwell
Automation products. To obtain a copy, contact your local Rockwell Automation
office or distributor.
How to Use this Manual
To use this manual effectively, use the worksheets provided in Appendix B. The
worksheets can help you document your application and settings and also facilitate
the flow of information to other individuals in your organization for
implementation.
For Read this document Publication Number
A BASIC and BASIC-T manual that provides
information on installing and using the 1746-BAS
and 1746-BAS-T modules.
SLC 500™ BASIC and BASIC-T Modules
User Manual
1746-UM004A-US-P
A programming manual with detailed
instructions on installing and using BASIC
Development Software to program the BASIC
and BASIC-T modules.
BASIC Development Software
Programming Manual
1746-PM001A-US-P
An overview of the SLC 500 family of products SLC 500™ System Overview 1747-SO001A-US-P
A description of how to install and use a Modular
SLC 500 Processor
Modular Hardware Style Installation and
Operation Manual
1747-6.2
A reference manual that contains status file data
and instruction set information for SLC 500
processors
SLC 500™ and MicroLogix™ 1000
Instruction Set Reference Manual
1747-6.15
A description of how to install and use a module
that acts as a bridge between DH485 networks
and devices requiring DF1 protocol.
DH-485/RS-232C Interface Module User’s
Manual
1747-6.12
An application example demonstrating how to
transfer ASCII data to an SLC 5/02 or later
processor using a remote SLC 500 BASIC module.
ASCII Data Transfer to the SLC 500™
BASIC Module (Series B)
1746-2.41
In-depth information on grounding and wiring
Allen-Bradley programmable controllers
Allen-Bradley Programmable Controller
Grounding and Wiring Guidelines
1770-4.1
A glossary of industrial automation terms and
abbreviations
Allen-Bradley Industrial Automation
Glossary
AG-7.1
An article on wire sizes and types for grounding
electrical equipment
National Electric Code Published by the National Fire Protection
Association of Boston, MA

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Terms and Abbreviations
The following terms and abbreviations are specific to this product. For a complete
listing of Allen-Bradley terminology, refer to the Allen-Bradley Industrial
Automation Glossary, publication number ICCG-7.1.
•Module SLC 500 BASIC and BASIC-T Modules (catalog numbers
1746-BAS and 1746-BAS-T)
•BASIC development software BASIC Development Software (catalog
number 1747-PBASE)
•BASIC —the BASIC-52 programming language
•console device — the device connected to the BASIC module program port.
This device is used as an interface between the user and the BASIC program.
•DH485 network communication protocol
•EPROM Erasable Programmable Read Only Memory
•EEPROM — Electrically Erasable Programmable Read Only Memory
•memory module — BASIC or BASIC-T modules EEPROM or UVPROM
•MTOP system control value that holds the last valid memory address
•program port — the port used to program the module. Either PRT1 or port
DH485 can be used as the program port.
•RAM — Random Access Memory
•ROM — Read Only Memory, refers to the optional memory module memory
space (EEPROM or UVPROM)
•RS-232/423 serial communication interface
•RS-422 differential communication interface
•RS-485 network communication interface
•SCADA — Supervisory Control and Data Acquisition
•scalar variable — a variable with a single value
•SLC 500 SLC 500 fixed and modular controller
•UVPROM — Ultra Violet Erasable Programmable Read Only Memory
Conventions Used in this
Manual
The following conventions are used throughout this manual:
•Bulleted lists such as this one provide information, not procedural steps.
•Numbered lists provide sequential steps or hierarchical information.
•Italic type is used for emphasis.
•Te x t i n this font indicates words or phrases you should type.
•Key names match the names shown and appear in bold, capital letters within
brackets (for example, [ENTER]).

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Rockwell Automation
Support
Allen-Bradley offers support services worldwide, with over 75 Sales/Support
Offices, 512 authorized Distributors and 260 authorized Systems Integrators
located throughout the United States alone, plus Rockwell Automation
representatives in every major country in the world.
Local Product Support
Contact your local Rockwell Automation representative for:
•sales and order support
•product technical training
•warranty support
•support service agreements
Technical Product Assistance
If you need to contact Rockwell Automation for technical assistance, please review
the information in the appropriate chapter first. Then call your local Rockwell
Automation representative.
Your Questions or Comments on this Manual
If you find a problem with this manual, please notify us of it on the enclosed
Publication Problem Report.
If you have any suggestions for how this manual could be made more useful to you,
please contact us at the address below:
Rockwell Automation
Control and Information Group
Technical Communication, Dept. A602V
P.O. Box 2086
Milwaukee, WI 53201-2086

Publication 1746-RM001A-US-P
P-6

1Publication 1746-RM001A-US-P
Chapter 1
Language Elements
This chapter introduces you to the elements of a BASIC program. These elements
include BASIC:
•line numbers
•statements, commands, and operators
•line length
Character Set
BASIC programs are composed of a group of BASIC program lines. Each BASIC
program line is composed of a group of ASCII characters. Refer to Appendix A for
a complete listing of ASCII character codes.
The BASIC Program Line
BASIC program lines consist of a BASIC line number and BASIC statements and
operators. BASIC program lines are restricted to the BASIC line length.
BASIC Line Numbers
We refer to BASIC line numbers as:
[ln num]
BASIC line numbers indicate the order that the program lines are stored in
memory and are also used as references when branching and editing. This number
may be any whole integer from 1 to 65535. Typically you start numbering BASIC
programs with line number 10 and increment by 10. This allows you to add
additional lines later as you work on your program.
Since the computer runs the statements in numerical order, additional lines need
not appear in consecutive order on the screen. If you enter line 35 after line 40, the
computer still runs line 35 after line 30 and before line 40. This technique saves
you from reentering an entire program if you forget to include a line.
IMPORTANT The first line of your program must be a comment.

Publication 1746-RM001A-US-P
1-2 Language Elements
Typically, the line numbers of a program start out looking like the first column and
end up looking something like the second column below:
#1 #2
10 5
20 7
30 10
40 15
50 20
60 30
70 35
80 40
..
..
..
BASIC Statements, Commands, and Operators
BASIC program lines consist of a BASIC line number and BASIC statements and
operators. Depending on the logic of your program, there may be more than one
statement on a line. If so, each must be separated by a colon (:).
BASIC Line Length
A BASIC program line always begins with a line number and must contain at least
one character, but no more than 68 characters. A program line ends when you press
[RETURN].
IMPORTANT Reuse of an existing line number causes all of the information
referenced by the original line number to be lost. Be careful
when entering numbers in the Command mode, as you may
accidentally erase some program lines. You may delete an
existing line by retyping it with no information following it and
pressing [RETURN].

1Publication 1746-RM001A-US-P
Chapter 2
Data Types
This chapter provides you a method of defining or displaying data within the
BASIC programming language through the use of:
•data types
•variables
Data Types
Data types are broken down into three sections: argument stack, string and
numeric elementary data types, and backplane conversion data.
Argument Stack
The argument stack (A-stack) stores all constants that the BASIC or BASIC-T
module is currently using. Operations such as add, subtract, multiply, and divide
always operate on the first two numbers of the argument stack and return the result
to the stack. The argument stack is 203 bytes long. Each floating point number
placed in the stack requires 6 bytes of storage. The argument stack can hold up to
33 floating point numbers before overflowing.
In addition, the PUSH command saves data to the argument stack and the POP
command restores data from the stack. PUSHes and POPs are typically associated
with CALLs. PUSHes and POPs are mechanisms used to transfer information to
and from CALL routines.
PUSH makes a copy of the variable being PUSHed, then puts that copy on the top
of the argument stack. POP takes the value on the top of the argument stack and
copies it to the variable being POPped.
String Data Types
A string is a character or group of characters stored in memory. Usually, the
characters stored in a string make up a word or a sentence. Strings allow you to use
characters instead of numbers. Strings are shown as:
$([expr])
The module uses single-dimension string variables, $([expr]). The dimension of
a string variable (the [expr] value) ranges from 0 to 254. This means that you can
define and manipulate 255 different strings in the module. Initially, no memory is
allocated for strings. Memory is allocated using the STRING statement. Strings are
declared and manipulated through the $ operator.

Publication 1746-RM001A-US-P
2-2 Data Types
When allocating memory for a string, you must account for the overhead bytes
used by BASIC to manipulate strings. BASIC uses one overhead byte per string
being declared plus one additional overhead byte.
Example 1
String 106,20
Allocates space for five 20 byte strings (100 bytes) and includes five overhead bytes
(1 per string) and one additional overhead byte.
In the module you can define strings with the LET statement, the INPUT
statement, and with the ASC operator.
Example 2
>10 STRING 106,20
>20 $(1)=“THIS IS A STRING, ”
>30 INPUT “WHAT’S YOUR NAME? - ”,$(2)
>40 PRINT $(1),$(2)
>50 END
READY
>RUN
WHAT’S YOUR NAME? - FRED
THIS IS A STRING, FRED
READY
>
You can also assign strings to each other with a LET statement.
Example 3
LET $(2)=$(1)
Result: Assigns the string value in $(1) to the STRING $(2).

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Data Types 2-3
Numeric Data Types
There are two different numeric data types:
•integer numbers
•floating-point numbers
You can enter and display numbers in four formats: integer, decimal, hexadecimal,
and exponential.
Example
129, 34.98, 0A6EH, 1.23456E+3
The BASIC or BASIC-T module interprets all numbers as floating-point numbers
except when performing logical operations. When performing logical operations,
the module converts floating-point numbers to integers, performs the operation,
then converts the result back to floating-point.
Integer Numbers
The module operates on unsigned 16-bit integers that range from 0 to 65535 or
0FFFFH. You can enter all integers in either decimal or hexadecimal format. You
indicate a hexadecimal number by placing the character H after the number
(example: 170H). If the hexadecimal number begins with A through F, then it
must be preceded by a zero. (For example, you must enter A567H as 0A567H.)
When an operator, such as .AND. requires an integer, the module truncates the
fraction portion of the number so it fits the integer format. Integers are shown as:
[integer]
Floating-Point Numbers
In the module, all numbers are stored as floating-point numbers. Floating-point
numbers are numbers in which the decimal point floats depending on the
significant digits of a specific number. The processor accounts for the location of
the decimal point. This allows the processor to store only the significant digits of a
value, thus saving memory space.
You can represent the following range of numbers in the module:
+1E –127 to +.99999999 +127
There are eight significant digits. Numbers are internally rounded to fit this
precision.
IMPORTANT The SLC 500 processor operates on signed 16-bit integers that
range from –32768 to 32767. If an integer value larger than
32767 is passed to the processor from the module, that value is
interpreted as negative by the processor.

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2-4 Data Types
Backplane Conversion Data
The module communicates with the local processor through the SLC 500 I/O
backplane. All data communicated to and from the SLC 500 is in SLC 500 format.
The SLC 500 formats are:
•16-bit signed integer (–32768 to 32767)
•16-bit binary (0000000000000000 to 1111111111111111)
Variables
Variables that include a single-dimension expression [exp] are dimensioned or
arrayed variables. Variables that contain a letter or a letter and a number are scalar
variables. Any variables entered in lower case are changed to upper case. Variables
are shown as:
[var]
The module allocates variables in a static manner, which means the first time a
variable is used, the module allocates a portion of memory (8 bytes) specifically for
that variable. This memory cannot be de-allocated on a variable to variable basis.
This means that if you execute a statement (example: >10 Q - 3), you cannot tell
the module that the variable Q no longer exists to free up the 8 bytes of memory
that belong to Q. You can clear the memory allocated to variables by executing a
CLEAR statement. The CLEAR statement frees all memory allocated to variables.
Variables may be set aside for reuse to save memory.
IMPORTANT Any integer larger than 32767 is interpreted as a negative number
by the SLC 500 processor
IMPORTANT The module requires less time to find a scalar variable because
there is no expression to evaluate. To run a program as fast as
possible, use single-dimension variables only when necessary. Use
scalar variables for intermediate variables and assign the final
result to a dimensioned variable. Also, put the most frequently
used variables first. Variables defined first require the least
amount of time to locate.