ICP DAS USA ET-2217CI, User Manual

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ET-2200 Series Ethernet I/O Modules
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6.2.1 01(0x01) Read the Status of the Coils
(Read DO Readback vaslues)
This function code is used to read either the current status of the coils or the current Digital
Output readback value from the ET-2200 series module.
[Request]
Byte Description Size Value
00 Net ID (Station Number) 1 Byte 1 to 247
01 Function Code 1 Byte 0x01
02-03 Starting DO Address 2 Bytes
Refer to Section 6.3 or 6.4 “Modbus Register
Table” to find the address.
Byte 02 = high byte
Byte 03 = low byte
04-05 Number of Points (Channels) 2 Bytes
Byte 04 = high byte
Byte 05 = low byte
[Response]
Byte Description Size Value
00 Net ID (Station Number) 1 Byte 1 to 247
01 Function Code 1 Byte 0x01
02 Byte Count 1 Byte
Byte Count of the Response
( n = (7)/8 )
03 Data n Bytes
n= 1; Byte 03 = data bit 7 to 0
n= 2; Byte 04 = data bit 15 to 8
.......
n= m; Byte m+2 = data bit (8m-1) to 8(m-1)
[Error Response]
Byte Description Size Value
00
Net ID (Station Number)
1 Byte 1 to 247
01
Function Code
1 Byte 0x81
02
Exception Code
1 Byte
Refer to the Modbus Standard Specifications for
more details