The exception code is used for the Modbus Slave node to send back packets so that the Modbus Master can get feedback.
－ The packet was successfully transferred.
－ The Slave device receives an unallowed function code.
－ The Slave device receives an unallowed address space.
－ The Slave device receives an unallowed value in the specified address space.
－ A non-recoverable error occurred during operation.
－ The instruction has been accepted and is being processed, but it will take a long time to complete.
－ Long command being processed.
－ Parity error detected when trying to read memory.
－ Unavailable Modbus Gateway paths.
－ Modbus Gateway devices are not on the network.
－ Invalid Slave Number.
－ Invalid Function Code.
－ Replies over time.
－ Ineffective cyclic redundancy checks.
－ Illegal data patterns.
－ Ineffective access.
The text of the 86Duino reference is a modification of the Arduino reference and is licensed under a Creative Commons Attribution-ShareAlike 3.0 License. Code samples in the reference are released into the public domain.