WAGO-I/O-SYSTEM 750
Fieldbus Communication 233
750-880, 750-880/025-000 ETHERNET Programmable Fieldbus Controller
Manual
Version 1.0.1
12.2.3.8 Function Code FC15 (Force Multiple Coils)
This function sets a sequence of output bits to 1 or 0 in a slave device. The
maximum number is 256 bits.
Request
The request message specifies the reference number (first coil in the sequence),
the bit count (number of bits to be written), and the output data. The output coils
are zero-based; therefore, the first output point is 0.
In this example 16 bits are set, starting with the address 0. The request contains 2
bytes with the value 0xA5F0, or 1010 0101 1111 0000 in binary format.
The first data byte transmits the value of 0xA5 to the addresses 7 to 0, whereby 0
is the lowest value bit. The next byte transmits 0xF0 to the addresses 15 to 8,
whereby the lowest value bit is 8.
Table 114: Request of Function code FC15
Byte
Field name
Example
Byte 0, 1
Transaction identifier
0x0000
Byte 2, 3
Protocol identifier
0x0000
Byte 4, 5
Length field
0x0009
Byte 6
Unit identifier
0x01 not used
Byte 7
MODBUS function code 0x0F
Byte 8, 9
Reference number
0x0000
Byte 10, 11
Bit count
0x0010
Byte 12
Byte count
0x02
Byte 13
Data byte1
0xA5
Byte 14
Data byte2
0xF0
Response
Table 115: Response of Function code FC15
Byte
Field name
Example
...
Byte 7
MODBUS function code 0x0F
Byte 8, 9
Reference number
0x0000
Byte 10, 11
Bit count
0x0010
