Ethernet I/O Modules
6.2.1 01 (0x01) Read the Status of the Coils (Readback DOs)
This function code is used to read either the current status of the coils or the current digital output
readback value from the PETL/tET/tPET 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 the Modbus Address Table for the
PETL/tET/tPET series.
Section 6.3 Modbus Register Table
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
ICP DAS CO., LTD.
PETL/tET/tPET DIO Series User Manual, Ver. 2.1, Sep. 2014, Page: 80
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