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7 Using Modbus-RTU Slave Mode
7-16
CJ-series Serial Communications Units Operation Manual for NJ-series CPU Unit(W494)
z
Function
Reads multiple words from the DM or EM Area of the memory used for CJ-series Unit.
z
Command
* The address depends on the area that is allocated.
z
Response
* N = Quantity of Registers
z
Reading 3 Words from DM 1000 to DM 1002
Read Holding Registers
Length
Data
Function Code
1 byte
03 hex
Starting Address
2 bytes
0000 to 7FFF hex (*)
Quantity of Regis-
ters
2 bytes
0001 to 007D hex
Length
Data
Function Code
1 byte
03 hex
Byte Count
1 byte
N
×
2 (*)
Register Value
N
×
2 bytes
Request
Response
Data
Data
Function Code
03 hex
Function Code
03 hex
Starting Address (H)
03 hex
Byte Count
06 hex
Starting Address (L)
E8 hex
Register Value (H) DM1000
AB hex
Quantity of Registers (H)
00 hex
Register Value (L) DM1000
12 hex
Quantity of Registers (L)
03 hex
Register Value (H) DM1001
56 hex
Register Value (L) DM1001
78 hex
Register Value (H) DM1002
97 hex
Register Value (L) DM1002
13 hex
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
DM1000
A
B
1
2
DM1001
5
6
7
8
DM1002
9
7
1
3