A
Are there any exceptions codes under Open Modbus that are valid if someone accidently attempts to write to a read-only register?
It seems under open modbus that there is no reference to 3xxxx and 4xxxx addresse like their used to be under standard Modbus. Because of this, it is relatively easy to attempt to write to a read-only address. I expect it is upto the slave device to reject the command and return an approproate error code. Looking through the Open Modbus Spec 1999, however, there does not seem to be an error code that says something like "Invalid operation on read-only register".
Currently existing exception codes like "Illegal Function" cannot be used because the write function is valid for the slave. "Invalid Data address" cannot be used because the data address is valid, it just so happens that it is a read-only address", and so on.
It seems under open modbus that there is no reference to 3xxxx and 4xxxx addresse like their used to be under standard Modbus. Because of this, it is relatively easy to attempt to write to a read-only address. I expect it is upto the slave device to reject the command and return an approproate error code. Looking through the Open Modbus Spec 1999, however, there does not seem to be an error code that says something like "Invalid operation on read-only register".
Currently existing exception codes like "Illegal Function" cannot be used because the write function is valid for the slave. "Invalid Data address" cannot be used because the data address is valid, it just so happens that it is a read-only address", and so on.