Modbus implementation
Modbus exception codes
Code | Name | Description |
---|---|---|
01 |
Illegal function |
The requested command is invalid. |
02 |
Illegal address |
This code indicates one of the following:
|
03 |
Illegal value |
This code indicates one of the following:
|
Modbus invalid read registers responses
Invalid type | Read response |
---|---|
Unmapped (unused)1 register |
0x8000 |
Reserved1 register responses by type |
|
Signed integer 16-bit |
0x8000 |
Unsigned integer 16-bit |
0xFFFF |
Signed integer 32-bits |
0x80000000 |
Unsigned integer 32-bits |
0xFFFFFFFF |
Signed integer 64-bits |
0x8000000000000000 |
Float32 |
0xFFC00000 (NaN = Not a number) |
1 IRIG-B can only be connected to one of the digital inputs located on the meter base, not an option module. Unmapped (unused) registers are registers that will never be used by the meter, and therefore have no defined format. Reserved registers have a defined format and are intended for use by the meter, its options or its variants. |
Modbus invalid write registers response
If the meter receives a write command to a Modbus register address that does not have a register mapped, the meter will not respond. No data is written or stored, and the meter will not send back a rejection to the request.
If the meter receives a write command to a read-only Modbus register address, exception code 3 (illegal value) is returned.
Fixed and configurable Modbus map
Your device has a fixed (static) register map for meter data and a flexible, user-configured register map.
Modbus security
Your meter’s onboard security options include Modbus-specific settings. These security settings may need to be configured in order to write Modbus data to the meter.