Rockwell Automation 1785-Lx0C15 ControlNet PLC-5 Programmable Controllers User Manual - Manual (Page 45)

1785-UM022C-EN-P - February 2008
Planning to Use Your ControlNet PLC-5 Processor 2-7
Using I/O Forcing Operations
ControlNet I/O forcing occurs in the same way as remote I/O forcing
in the ControlNet processors. The processor performs the forcing and
transmits the forced data to the output- and input-image tables. You
can force any discrete I/O data placed in the I/O image; however,
forcing of DIF and DOF data is not supported.
For detailed information about forcing, see your programming
software documentation.
Peer-to-peer
Messaging
MSG Instructions
You can use ControlNet message (MSG) instructions and the data-type
MG to create unscheduled messages that are initiated by one ControlNet
PLC-5 processor and sent to another ControlNet PLC-5 processor. The
MG data type for the ControlNet instruction has the following
information:
• Command—PLC-5 TYPED READ, PLC-5 TYPED WRITE, PLC-3 WORD
RANGE READ, PLC-3 WORD RANGE WRITE, PLC-2 UNPROTECTED
READ, PLC-2 UNPROTECTED WRITE
• Data-table address in source processor
• Size of message in elements
• Network address of destination processor
• Data-table address in destination processor
• Port number—set to 2 for the ControlNet network
• Flags:
.TO forces a message to time out
.EW indicates that the message is waiting for an open connection
.CO message is sent continuously in Run mode
.ER indicates that the message was terminated due to an error
.DN indicates that the message was sent without error
.ST indicates that the message was started
.EN indicates that the message instruction is enabled
.NC forces the connection to close when the message is done
• Error code—indicates the error when the.ER bit is set 2
• As many as 32 ControlNet MSGs can be active
at a time 1
• Minor fault bit S:17/13 is set when 32
ControlNet MSGs are active at a time
• All messages have the same priority
• No message is initiated when the processor is
in Program mode
• Messages that have been running with the.CO
bit set automatically restart on the Program-
to-Run transition when the Continue Last step
bit is set and the data table has not changed
• Each message has a maximum size of 1000
elements
See chapter 4 and Appendices C and F for more
information.
1 Because connections are opened and closed as needed, more can exist in a program as long as no more than this number are active at one time.
2 See Appendix D for a list of ControlNet error codes.
Operation Description Features