Force Multiple Coils (Function Code 15) - ProSoft Technology MVI56E-MNETC User Manual

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User Manual

5.4.10 Force Multiple Coils (Function Code 15)

Query
This function forces each coil (Modbus 0x range) 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 server address 0 (Broadcast Mode) forces all
attached servers to modify the desired coils.
Note: Functions 5, 6, 15, and 16 are the only messages (other than Loopback Diagnostic Test) that
are 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.
Note: This is the structure of the message being sent out to the Modbus network. The byte values
below are in hexadecimal display.
Node Func
Address Code
0B 0F
Response
The normal response is an echo of the server address, function code, starting
address, and quantity of coils forced.
Node Func
Address Code
0B 0F
Writing to coils with Modbus function 15 is accomplished regardless of whether
the addressed coils are disabled or not.
Page 144 of 172
Modbus TCP/IP Client Enhanced Communication Module - Client/Server
Coil Coil Number of
Coils High
Address Address
High Low
00 13 00
Coil Coil Number of
Address Address Coils High
High Low
00 13 00
MVI56E-MNETC/MNETCXT ♦ ControlLogix Platform
Number of Byte Force
Coils Low Count
Data High
20 to 27
0A 02 CD
Number of Error Check
Coils Low Field (2 bytes)
0A CRC
Force Error Check
Field (2 bytes)
Data Low
28 to 29
01 CRC
ProSoft Technology, Inc.
September 20, 2018