Delta RMC101 - Manual (Page 505)

Serial (RS-232/422/485) 5.5
Communications 5-255
500CPU Read, or 500CPU Write. The type of PLC selected is not important, but the
Read or Write determines whether you will read registers from the RMC or write
registers into the RMC.
• Data Table Address: Enter the address of the first Allen-Bradley PLC register to read
RMC registers into, or to write to RMC registers from.
• Size in Elements: Enter the number of RMC registers to read or write in this field. The
MicroLogix can transfer 1 to 41 integers.
• Channel: Set this to the channel number of the serial port you want to use. The
MicroLogix 1500 LRP Series B can use either channel 0 or 1, but all other MicroLogix
PLCs will always use channel 0.
• Target Device: This section holds parameters for the target device.
• Message Timeout: Indicate the number of seconds to wait for the RMC to respond
before determining that the attempt failed. This can be set as low as a few seconds.
• Data Table Address: Enter the address of the first RMC register to read or write in this
field. See the RMC Register Map (Allen-Bradley) for help on addresses.
• Local Node Addr (dec): Enter the node address of this RMC. The node address of the
RMC is set up in the Serial Module Options dialog box, which is described in
Configuring the RMC SERIAL. The node address entered on that screen is in decimal,
so it is recommended that you enter the same number in the dec field.
• Local/Remote and Bridge Parameters: In most applications these will be set to Local
and there will be no bridge parameters. If you are using a bridge then these parameters
will need to be used. However, this is beyond the scope of RMC documentation. Refer
to your Allen-Bradley documentation for instructions on using these fields.
Using the MSG Block in Ladder Logic
The Allen-Bradley MSG block takes multiple ladder scans to complete. Therefore, it is important
to enable the MSG block for the correct amount of time. Specifically, the MSG block must be
energized until the message control's enable (EN) bit turns on. Delta has found some aspects of
this to be difficult and therefore has provided the following ladder samples:
Read or Write Continuously
Using the Examine If Open instruction as shown below fulfills two requirements of continuous MSG
transactions. First, it will keep the block energized until the EN turns on, and second, it de-energizes
the MSG block once the transactions is started so that when the transaction is completed (EN goes
low again), the MSG block sees a rising edge on its input, thus repeating the transaction: