ProSoft Technology MVI56E-MCMR - Manual (Page 165)

MVI56E-MCMR ♦ ControlLogix Platform Reference
Modbus Communication Module with Reduced Data Block User Manual
ProSoft Technology, Inc. Page 165 of 225
May 13, 2014
Block Response from Module to Processor
Word Offset Data Field(s) Description
0 Number of Slaves
to report This field always receives a value of 248 (-8 as a
signed SINT, 16#F8). A status word for all potential
Modbus Slave Device Addresses will be included in
the returned data.
1 Start index of first
Slave This field is always 0. All 248 potential Modbus Slave
Device Addresses will have a corresponding Status
Word in the returned data.
2 to
39
Slave Status List
data 0 The Slave is inactive, not currently the slave
being actively polled, waiting for its turn to be
polled, or not a Modbus Slave Device Address
used in the Command List for the Master port.
1 The Slave at this specific address is the one
currently being polled or controlled by the
Master port. This does not indicate that the
Slave has responded to a poll request; only
that the Master is currently trying to poll this
Slave.
2 The may be thought of as a "Slow Poll" mode,
whereby a Slave with communications errors
will be polled at a lower-than-normal
frequency. This status is set by the Master
port whenever it has failed to communicate
with the Slave device and the Port
configuration parameter, E
RROR D ELAY
C OUNTER , has been set greater than 0.
The following illustration shows the MSG instruction configuration for a block of
this type.