Rockwell Automation 57C442 Data Highway Plus Interface Module - Manual (Page 25)

4-7
The format for the IODEF statement (used only in V2.1 and earlier) is
as follows:
nnnn lODEF variable name [SLOT=slot number, &
REGISTER=register number, BIT=bit number]
where:
nnnn = configuration task line number
variable_name = integer or boolean variable. Double integer
variables can beused but should be avoided because of the
possibility that all 32 bits will not transfer in one operation.
slot number = slot number of the Data Highway Plus Interface
module in the rack. This number may range from 0 to 15.
register number = Multibus register number on the Data Highway
Plus Interface module. Register numbers correspond to 16-bit
words on the module.
bit number = bit number of the I/O point in the register. Bit
numbers range from 0 to 15. Bit numbers are specified for boolean
variables only.
Any variables contained in the rack configuration are accessible by any
task on any AutoMax Processor in the rack. When AutoMax variables
are referenced in AutoMax tasks, the data is directly obtained from or
written to the register image on the module. The data storage for an
AutoMax variable mapped to an A-B
TM register will always exist in the
Data Highway Plus module’s dual port memory.
The registers in the Data Highway Plus Interface module’s A-B register
image may be displayed using the AutoMax Programming Executive
Monitor I/O function. Refer to Appendix I for the method used to convert
A-8 register numbers so that they can be viewed using the monitor.
WARNING
IF YOU USE DOUBLE INTEGER VARIABLES IN THIS INSTANCE, YOU
MUST IMPLEMENT A SOFTWARE HANDSHAKE BETWEEN THE
TRANSMITTER AND RECEIVER TO ENSURE THAT BOTH THE LEAST
SIGNIFICANT AND MOST SIGNIFICANT 16 BITS HAVE BEEN
TRANSMITTED BEFORE THEY ARE READ BY THE RECEIVING
APPLICATION PROGRAM. FAILURE TO OBSERVE THIS PRECAUTION
COULD RESULT IN BODILY INJURY.