ProSoft Technology MVI69-PDPMV1 - Manual (Page 177)

MVI69-PDPMV1 ♦ CompactLogix or MicroLogix Platform Reference
PROFIBUS DPV1 Master User Manual
ProSoft Technology, Inc. Page 177 of 225
July 8, 2011
Mailbox Communication
Note: The module cannot keep track of multiple mailbox requests. Therefore, only one mailbox
request can be active at any time. It is up to the customer to write his or her mailbox message logic
in such a way that a previous mailbox request has been responded to before a new mailbox
request is generated. The module will resume normal backplane transfer activity after sending a
mailbox request and while waiting for the slave's response, so as not to unduly slow down cyclic
data updates while doing mailbox messaging.
The processor requests a mailbox block by sending a block with a block number
between 100 and 109 for block size 240 words, between 100 and 101 for block
size 120 words and between 100 and 102 for block size 60 words. The request
block contains the mailbox request according to the data listed in Output Mailbox
(page 178).
The module immediately responds with a confirmation message consisting of the
Mailbox Out Message Response block to the processor, containing the same
block ID as the request block.
After the module processes the mailbox request, it sends the Mailbox In
Message block to the processor. Note that because the block ID will not
necessarily be the same as the one used during the mailbox request, the ladder
should refer to the command data to copy the mailbox response to the correct
controller tag. For example:
command = 02 => Set Operating Mode Response 1