Omron NV3Q Series, Connection Manual

Page: 125 / 145

101
Modbus Slave (RTU Mode)
Section 11-1
11-1-2 Function Code Reference
Provide an interval of at least the time required for four characters between
messages with Modbus slave (RTU Mode).
Function Code 01: Read internal bit status
■
Commands
■
Responses
PT slave
address Function
code
01 hex First address,
upper byte First address,
lower byte No. of bits to
read,
upper byte No. of bits 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
01 hex Number of
bytes Data byte 1
• • • • • • • • • •
Data byte n Error check,
upper byte Error check,
lower byte
1 byte 1 byte 1 byte 1 byte 1 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 01 hex.
First address Specify the address of the first bit to read in hexadecimal.
For GR20, specify 00 hex, 20 hex.
No. of bits to read Specify the number of bits to read in hexadecimal.
For 37 bits, specify 00 hex, 25 hex.
Up to 2,040 bits can be specified. (Specify 07 hex, F8 hex.)
Number of data
bytes The number of bytes from data byte 1 to data byte n is returned.
Byte 1 to n The ON/OFF status of the coils starting from the first coil are
returned in units of 8 bits. LSB of byte 1 is the status of the first bit.
Status is returned in units of 8 bits. Bits in byte n that do not corre-
spond to specified bits will be returned as 0.
Error check The CRC-16 values are sent and received.