Rockwell Automation 1785-Vx0B, D17856.5.9 PLC-5 VME VMEbus Programmable Controllers User Manual - Manual (Page 48)

4 Chapter
4-1
Ladder-Program Interfaces
Read this chapter to help you understand how to interact with the VMEbus
environment from your ladder program.
The PLC-5/VME processor allows ladder programs to perform direct
VMEbus read and write operations as well as to generate VMEbus
interrupts through the MSG instruction. This is the same data instruction
that is used for Data Highway, and it is programmed the same way. Four
messages are available:
Copy to VME
Copy from VME
Send VME interrupt
Check VME status file
To enter a VME message instruction, use your programming software to
edit the MSG control block. You will need to do the following:
specify a control block address for the MSG instruction
select ASCII as the message type
Important: You cannot use indirect addresses for the control-block
address in an MSG instruction.
enter channel 3A as the channel/port number
enter the appropriate VME command and accept the parameters you’ve
entered in the software
An internal processor interprets the ASCII string entered to determine the
VME operation to complete. The syntax for the ASCII strings is
as follows:
Chapter Objectives
Ladder Messages