Omron NV3W Connection Manual page 143

Modbus Slave (RTU Mode)
Function Code 04: Read holding register contents
■ Commands
PT slave Function
address code
04 hex
1 byte 1 byte
■ Responses
PT slave Function
address code
04 hex
1 byte 1 byte
Error check, Error check,
upper byte lower byte
1 byte 1 byte
First address, First address,
upper byte lower byte
1 byte 1 byte
Number of Register 1,
bytes upper byte
1 byte 1 byte
Item
PT slave address Specify the slave address of the PT to which to send the message.
For slave address 20, specify 14 hex.
Function code Specify 04 hex.
First address Specify the address of the first data register to read in hexadecimal.
For GDT108, specify 00 hex, 6C hex.
No. of registers to Specify the number of data registers to read in hexadecimal.
read For 5 registers, specify 00 hex, 05 hex.
Up to 127 registers can be specified. (Specify 00 hex, 7F hex.)
Number of The number of bytes from register 1 to register n is returned.
bytes
Register 1 to n The contents of the first data register is returned with the upper
byte first, followed by the lower byte. The contents of the specified
number of registers are returned.
Error check The CRC-16 values are sent and received.
Additional Information
Different function codes are used to read holding registers and input registers
with Modbus communications. When reading internal memory in the PT, either
function code can be used. The same area will be read.
No. of regis- No. of regis-
ters to read, ters to read,
upper byte lower byte
1 byte 1 byte
Register 1,
lower byte • • • • • • • • • •
1 byte
Function
Section 11-1
Error check, Error check,
upper byte lower byte
1 byte 1 byte
Register n, Register n,
upper byte lower byte
1 byte 1 byte
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