GE 350 Communications Manual page 150

FUNCTION CODE 03H
8-2
SLAVE RESPONSE
SLAVE ADDRESS
FUNCTION CODE
BYTE COUNT
DATA 1 (see definition above)
DATA 2 (see definition above)
DATA 3 (see definition above)
CRC
Query:
The query message specifies the starting register and quantity of registers to be read.
Registers are addressed starting at zero: registers 1 to 16 are addressed as 0 to 15.
Here is an example of a request to read registers 40172 to 40175 from slave device 254:
Field Name
Slave Address
Function
Starting Address Hi
Starting Address Lo
No. of Points Hi
No. of Points Lo
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.
The response is returned when the data is completely assembled.
Field Name
Slave Address
Function
Byte Count
Data Hi (Register 40172)
Data Lo (Register 40172)
Data Hi (Register 40173)
Data Lo (Register 40173)
Data Hi (Register 40174)
Data Lo (Register 40174)
Data Hi (Register 40175)
Data Lo (Register 40175)
The contents of register 40172 are shown as the two byte values of 00 FE hex, or254
decimal. The contents of registers 40173 to 40175 are 00 04, 00 00 and 00 00 hex, or 4, 0
and 0 decimal.
BYTES EXAMPLE
1 11
1 03
1 06
2 02 2B
2 00 00
2 00 64
2 54 83
Hex
FE
03
00
AB
00
04
Hex
FE
03
08
00
FE
00
04
00
00
00
00
SR3 SERIES PROTECTIVE RELAY PLATFORM – COMMUNICATIONS GUIDE
CHAPTER 8: MODBUS FUNCTIONS
DESCRIPTION
message from slave
17
read registers
3 registers = 6 bytes
value in address
006B
value in address
006C
value in address
006D
CRC error code