Azbil C1M - Page 234

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Chapter 8. Modbus Communication Function
• Abnormal termination
3AH 30H 41H 38H 34H 30H 31H 37H 31H 0DH 0AH
: 0 A 8 4 0 1 7 1 CR LF
(1) (2) (3) (4) (5) (6)
(1) Start of the message
(2) Station address
(3) Error flag (Since undefined “04” was sent as a command with an instruction
message, the most significant bit was turned ON and “84” was returned.)
(4) Termination code indicating error (
Page 8-8)
(5) Checksum (LRC)
(6) Delimiter
Modbus/RTU
• Normal example
0AH 03H 04H 03H 01H 00H 03H 51H 76H
(1) (2) (3) (4) (5) (6)
(1) Station address
(2) Read command (03H)
(3) Read data count × 2 (bytes)
(4) Read data 1
(5) Read data 2
(6) Checksum (CRC)
• Abnormal termination
0AH 84H 01H F3H 02 h
(1) (2) (3) (4)
(1) Station address
(2) Error flag (Since undefined “04H” was sent as a command with an instruction
message, the most significant bit was turned ON and “84H” was returned.)
(3) Termination code indicating error (
Page 8-8)
(4) Checksum (CRC)