Basic Formats - Omron NV3Q Connection Manual

Modbus Slave (RTU Mode)

11-1-1 Basic Formats

Commands
PT slave address Function code
Responses
PT slave address Function code
The formats for sending commands from the Modbus-RTU master to the PT
and for returning responses from the PT are given below. The maximum
length of commands or responses supported by the NV-series PTs is 512
bytes.
Data
Data
■
PT Slave Address
Specify the slave address set in the PT (1 to 247). However, a maximum of 31
PTs can be connected. The Modbus-RTU master can communicate with only
one PT at a time. The slave address can be set to 0 for some function codes
to specify broadcast mode. If 0 is specified, the command will be received by
all slaves regardless of their specified slave numbers. Responses are not
returned for broadcast commands.
■ Function Code
The function to be executed by the Modbus-RTU master is specified with the
function code. The NV-series PTs support the following function codes.
Function
code (hex)
01 Read internal bit status
03 Read holding register con-
tents
04 Read input register contents
05 Write single internal bit
06 Write data register, one word
0F Write multiple internal bits
10 Write multiple data registers
■ Data
The data required for the command is sent. The data that is required depends
on the function code.
■
Error Check
CRC-16 (cyclic redundancy check) error checking is performed.
Error check
Error check
Function Broadcast
mode
Supported. GR/WGR
Supported. GDT
Supported. GR
Supported. GDT
Section 11-1
Applicable internal
memory specifications
GR/WGR
GDT
GDT
99