Omron NV3Q Series, Connection Manual

Page: 123 / 145

99
Modbus Slave (RTU Mode)
Section 11-1
11-1-1 Basic Formats
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.
Commands
Responses
■
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.
■ 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.
PT slave address Function code Data Error check
PT slave address Function code Data Error check
Function
code (hex)
Function Broadcast
mode
Applicable internal
memory specifications
01 Read internal bit status GR/WGR
03 Read holding register con-
tents GDT
04 Read input register contents GDT
05 Write single internal bit Supported. GR/WGR
06 Write data register, one word Supported. GDT
0F Write multiple internal bits Supported. GR
10 Write multiple data registers Supported. GDT