Fieldbus
Communication
•
225
MODBUS
Functions
WAGO-I/O-SYSTEM 750
BACnet/IP Controller
4.3.3.8 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 se-
quence), 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 con-
tains 2 bytes with the value 0xA5F0, or 1010 0101 1111 0000 in binary for-
mat.
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 ad-
dresses 15 to 8, whereby the lowest value bit is 8.
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
Byte
Field name
Example
.....
Byte 7
MODBUS function code
0x0F
Byte 8, 9
Reference number
0x0000
Byte 10, 11 Bit Count
0x0010
Exception
Byte
Field name
Example
.....
Byte 7
MODBUS function code
0x8F
Byte 8
Exception code
0x01 or 0x02
Содержание 750-830
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