Omron NV3Q Series, Руководство по подключению

Страница: 127 / 145

103
Modbus Slave (RTU Mode)
Section 11-1
Function Code 04: Read holding register contents
■ Commands
■
Responses
PT slave
address Function
code
04 hex First address,
upper byte First address,
lower byte No. of regis-
ters to read,
upper byte No. of regis-
ters to read,
lower byte Error check,
upper byte Error check,
lower byte
1 byte 1 byte 1 byte 1 byte 1 byte 1 byte 1 byte 1 byte
PT slave
address Function
code
04 hex Number of
bytes Register 1,
upper byte Register 1,
lower byte
• • • • • • • • • •
Register n,
upper byte Register n,
lower byte
1 byte 1 byte 1 byte 1 byte 1 byte 1 byte 1 byte
Error check,
upper byte Error check,
lower byte
1 byte 1 byte
Item Function
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
read Specify the number of data registers to read in hexadecimal.
For 5 registers, specify 00 hex, 05 hex.
Up to 127 registers can be specified. (Specify 00 hex, 7F hex.)
Number of
bytes The number of bytes from register 1 to register n is returned.
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.