IDEC High Performance Series - Manual (Page 641)

623
1 Modbus
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External Device Setup Manual
- FC1 Read coils - Reading of Coil (C) consecutively
Normal response
Byte 7 FC (Function code) = 10(HEX)
Byte 8-9 Reference No.
From Byte 10 Number of write words
Abnormal response
Byte 7 FC (Function code) = 90 (HEX)
Byte 8 Exception code 01 or 02
Example
Writing to HR400001 (1 word). The write value is 1234 (HEX).
10 00 00 00 01 02 12 34 => 10 00 00 00 01
Request
Byte 7 FC (Function code) = 01
Byte 8-9 Reference No.
Byte 10-11 Number of read bits (1 to 2000 bits)
Normal response
Byte 7 FC (Function code) = 01
Byte 8 Number of bytes for the response ((number of read bits +7)/8)
From Byte 9 Read data
Abnormal response
Byte 7 FC (Function code) = 81 (HEX)
Byte 8 Exception code 01 or 02
Example
Reading of C1. 1 bit. The read value is 1.
01 00 00 00 01 => 01 01 01