Omron NV3W Connection Manual page 140

Modbus Slave (RTU Mode)
Error Responses
PT slave address Function code
No Responses
118
If there is an error in a data message that is sent, the PT will do nothing
except return the following message.
Data
Function code + 80 hex
The Modbus-RTU master can check the function code in the response mes-
sage to see if the data that was sent was correct. If an error occurs, the mas-
ter can check the error code to confirm the cause of the error.
Code number
ER01 There is an error in the function code.
(An unsupported function code was sent.)
ER02 There is an error in the address of an internal bit or data register.
(The address is out of range.)
ER03 There is an error in the number of internal bits or data registers.
(The number of bits or registers is out of range.)
The specified number of data items does not match the number
that was sent.
The data was not 0000 or FF00 hex for function code 05.
The specified number of data items to read caused the response
to exceed 512 bytes.
In the following cases, the PT will ignore the command and will not return a
response. If the slave address is 0 for write function codes, no response will
be returned.
1. If a transmission error is detected in the command. (Transmission errors
include overrun, framing, parity, and CRC-16 errors.)
2. If the slave address of the PT does not match the address specified in the
command.
3. If the time between data elements in the command is too long. (If the time
between data elements is more than the time required for 24 bits.)
Error check
Meaning
Section 11-1