GE PACSystems RX7i Reference Manual

Chapter 6. Serial I/O, SNP & RTU Protocols
GFK-2222AD April 2018 249
Message (23): Read Write 4x Memory
Performs a combination of one read and one write operation in a single Modbus transaction. The function
can write new contents to a group of 4x registers, and then return the contents of another group of 4x
registers. Broadcast is not supported.
Query:
The query specifies the starting address and quantity of registers of the group to be read. It also specifies
the starting address, quantity of registers, and data for the group to be written. The Byte Count field
specifies the quantity of bytes to follow in the Write Data field.
Here is an example of a query to read six registers starting at register 5, and to write three registers
starting at register 16, in slave device 17:
Field Name
Example
(Hex)
Slave address
11
Function
17
Read Reference Address Hi
00
Read Reference Address Lo
04
Quantity to Read Hi
00
Quantity to Read Lo
06
Write Reference Address Hi
00
Write Reference Address Lo
0F
Quantity to Write Hi
00
Quantity to Write Lo
03
Byte Count
06
Write Data 1 Hi
00
Write Data 1 Lo
FF
Write Data 2 Hi
00
Write Data 2 Lo
FF
Write Data 3 Hi
00
Write Data 3 Lo
FF
Error Check (LRC or CRC)
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GE PACSystems RX7i Specifications

General

Brand	GE
Model	PACSystems RX7i
Category	Controller
Language	English