PACSystems™ RX3i and RSTi-EP CPU Reference Manual Section 6
GFK-2222AK October 2019
Serial I/O, SNP & RTU Protocols 183
Note: If the Or_Mask value is zero, the result is simply the logical ANDing of the current contents
and And_Mask. If the And_Mask value is zero, the result is equal to the Or_Mask value.
Note: The contents of the register can be read with the Read Holding Registers function (function
code 03). They could, however, be changed subsequently as the controller scans its user logic
program.
Example of a Mask Write to register 5 in slave device 17, using the above mask values:
6.3.3.12.2 Response:
The normal response is an echo of the query. The response is returned after the register
has been written.
6.3.3.13 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.
6.3.3.13.1 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:
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