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CALL PLCREAD Statement
Purpose:
This command is used to read the value(s) in a PLC’s registers, the status of
bits, or any other accessible memory location within the PLC. Refer to the
-PL5 and -SL5 for information on how to use this command with the
Allen-Bradley PLC-5 and SLC-500 processors.
Syntax:
CALL PLCREAD(id,cmd,start address,# ofregisters/bits,variable/array)
Comments:
id specifies the address of the PLC from which you wish to read data. This
number is usually 1 when interfacing to one PLC.
cmd specifies the read operation you wish to perform. See the table below for
the read operation possibilities.
start address is the starting address of the bit(s) or register(s) you are
interested in reading. In the case of the PLC interfaces implemented so far,
this does not include a data type specifier (%, $, !, etc.)
MOD GE9 TI3 TI5 OM1 PL2 Cmd Function Typical Data/Response*
• • • • • 1 Read PLC CPU Status 2 words; ID, run status
• • • • • • 2 Read Discrete Input Status 1 word per 16 bits
• • • • • • 3 Read Discrete Output Status 1 word per 16 bits
• • • • • • 4 Read Register 1 word per register
• 5 Read Input Register 1 word per register
• 6 Quick Status 1 word with 8 bits
• • 7 Read Analog Inputs 1 word per register
• • 8 Read Analog Outputs 1 word per register
• • 9 Read Discrete Internals/Coils/Relays 1 word per 16 bits
• 10 Read Holding Relays 1 word per 16 bits
• 11 Read Auxilary Relays 1 word per 16 bits
*The Data/Response format described here is typical. Refer to the section regarding your specific interface for
Table 5
Read Operation Options
PLC Interface Commands CALL PLCREAD Statement
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