01) Read Coils - ICP DAS USA IR-310-RM User Manual

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5.1 FC01 (0x01) Read Coils
This FC01 can read multiple relay states (ON/OFF, i.e. NO/NC). It is necessary to
append 2 bytes of CRC16 to the tail of each Modbus command.
‧Request
Byte order Item
00 Address
01 Function code
02 ~ 03 Starting channel
numbers
04 ~ 05 Output channel
quantity
‧Response
Byte order Item
00 Address
01 Function code
02 Byte count
03 Relay status (low
byte)
04 Relay status (high
byte)
* It depends on start channel number and output channel quantity.
Bit 0 is the ON/OFF state of the relay 0 where value = 1 means ON and value = 0
means OFF.
Example:
Read the state of the RL0 ~ RL9.
Request (hex): 01 01 00 00 00 0A BC 0D ("BC 0D" is CRC16)
where 00 00: Starting channel number is relay 0.
00 0A: Output channel quantity is 10. Get states of 10 relays.
Response (hex): 01 01 02 D5 00 E7 6C ("E7 6C" is CRC16)
where 02: Byte count is 2. 10 relay states need 2 bytes to get back the states.
D5 00: Relay status. D5 is the low byte for RL0 to RL7. 00 is the high byte for
RL8 and RL9.
IR-310-RM, IR Controlled 10-ch High Power Relay Module (Ver. 1.1, Jul/02/2013) 30
Size Value
1 Byte 1 ~ 247
1 Byte 0x01
2 Bytes 0x0000 ~ 0x000A
2 Bytes 0x0000 ~ 0x000A
Size Value
1 Byte 1 ~ 247
1 Byte 0x01
1 Bytes 1 or 2
1 Byte 0x00 ~ 0xFF. (*)
1 Byte 0x00 ~ 0x03. (*)