Function 0X02 - Read Discrete Inputs - Protech Systems SI-W509 User Manual

4.2.2 Function 0x02 – Read Discrete Inputs
This function code is used to read the current digital input value of SI-W509
module.
Request
Offset Description
00 Slave ID address
01 Function Code
02 ~ 03 Channel address
04 ~ 05 CRC
Response-1
The channel address is 0x2000~0x2004, 0x2140~0x2144, 0x2180~0x2184,
0x21C0~0x21C4 and 0x2200 ~0x2204.
Offset Description
00 Slave ID address
01 Function Code
02 Byte Count
03 Readback value
04 ~ 05 CRC
Response-2
For channel address is 0x2040~0x2050.
Offset Description
00 Slave ID address
01 Function Code
02 Byte Count
03 ~ 06 Readback value
07~ 08 CRC
SI-W509 SERIES USER MANUAL
Chapter 4 MODBUS RTU Protocol
Counts
1 Byte 1 to 255
1 Byte 0x02
2 Bytes
•
0x2000~0x2004: Digital Input
Chanel Value
•
0x2040~0x2050: Counter Value of
Digital Input Channel
•
0x2140~0x2144: Clear Counter
Value of Digital Input Channel
•
0x2180~0x2184: "high latch"
status of Digital Input Channel
•
0x21C0~0x21C4: "low latch"
status of Digital Input Channel
•
0x2200 ~0x2204: Clear latched
status of Digital Input Channel
2 Bytes Produced by utility.
Counts
1 Byte 1 to 255
1 Byte 0x02
1 Byte 1
1 Bytes The Value of Digital Input Channel
2 Bytes Produced by firmware.
Counts
1 Byte 1 to 255
1 Byte 0x02
1 Byte 4
4 Bytes The Value of Digital Input Channel
2 Bytes Produced by firmware.
Data
Data
Data
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