0X17) Read/Write Multiple Registers; Error Response - Hitachi HX-RIO3 Series User Manual

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6.2.10. 23 (0x17) Read/Write Multiple Registers

This function code performs a combination of one read operation, and one write operation in a single
MODBUS transaction. The write operation is performed before the read. The request specifies the starting
address and number of holding registers to be read as well as the starting address, number of holding
registers, and the data to be written. The byte count specifies the number of bytes to follow in the write data
field. The normal response contains the data from the group of registers that were read. The byte count field
specifies the quantity of bytes to follow in the read data field.
- In case of address 0x0800, 0x0801 output register value: 0x0000, 0x0000 changes to 0x1122, 0x3344.

6.2.11 Error Response

In an exception response, the server sets the MSB of the function code to 1. This makes the function code
value in an exception response exactly 80 hexadecimal higher than the value would be for a normal response.
•Exception Response Example
• Request
Field name
Function Code
Read Starting Address Hi
Read Starting Address Lo
Quantity of Read Hi
Quantity of Read Lo
Write Starting Address Hi
Write Starting Address Lo
Quantity of Write Hi
Quantity of Write Lo
Byte Count
Write Reg. Value#0 Hi
Write Reg. Value#0 Lo
Write Reg. Value#1 Hi
Write Reg. Value#1 Lo
• Response
Field name
Function Code
Byte Count
Read Reg. Value#0 Hi
Read Reg. Value#0 Lo
Read Reg. Value#1 Hi
Read Reg. Value#1 Lo
Field name
Function Code
Exception Code
Example
0x17
0x08
0x00
0x00
0x02
0x08
0x00
0x00
0x02
0x04
0x11
0x22
0x33
0x44
Example
0x0F
0x04
0x11
0x22
0x33
0x44
Example
0x81
0x02
HX-RIO3 Series