GE AF-600 FP Design Manual page 126

6.10.4 Read Holding Registers (03 HEX)
Description
This function reads the contents of holding registers in the slave.
Query
The query message specifies the starting register and quantity of registers to be read. Register addresses start at zero, i.e. registers 1-4 are addressed as 0-3.
Example: Read par. F-53 Maximum Reference, register 00530.
Field Name
Slave Address
Function
Starting Address HI
Starting Address LO
No. of Points HI
No. of Points LO
Error Check (CRC)
Response
The register data in the response message are packed as two bytes per register, with the binary contents right justified within each byte. For each register, the
first byte contains the high order bits and the second contains the low order bits.
Field Name
Slave Address
Function
Byte Count
Data HI
(Register 530)
Data LO
(Register 530)
Data HI
(Register 531)
Data LO
(Register 531)
Error Check
(CRC)
Example (HEX)
01
03 (read holding registers)
02 (Register address 529)
11 (Register address 529)
00
02 - (Par. F-53 is 32 bits long, i.e. 2 registers)
-
Example (HEX)
01
03
04
00
16
E3
60
-
AF-600 FP Design Guide
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