MVI56E-MCMR ♦ ControlLogix Platform Reference
Modbus Communication Module with Reduced Data Block User Manual
ProSoft Technology, Inc. Page 185 of 223
The data fields in responses to other kinds of queries could contain error counts
or other data requested by the sub-function code.
6.6.9 Force Multiple Coils (Function Code 15)
Query
This message forces each coil in a consecutive block of coils to a desired ON or
OFF state. Any coil that exists within the controller can be forced to either state
(ON or OFF). However, because the controller is actively scanning, unless the
coils are disabled, the controller can also alter the state of the coil. Coils are
numbered from zero (coil 00001 = zero, coil 00002 = one, and so on). The
desired status of each coil is packed in the data field, one bit for each coil (1=
ON, 0= OFF). The use of Slave address 0 (Broadcast Mode) will force all
attached Slaves to modify the desired coils.
Note: Functions 5, 6, 15, and 16 are the only messages (other than Loopback Diagnostic Test) that
will be recognized as valid for broadcast.
The following example forces 10 coils starting at address 20 (13 HEX). The two
data fields, CD =1100 and 00 = 0000 000, indicate that coils 27, 26, 23, 22, and
20 are to be forced on.
Data Coil Status
20 to 27
Data Coil Status
28 to 29
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