Modbus implementation

Your meter's Modbus implementation includes exception codes, invalid register responses, fixed and configurable register maps, and security.

Modbus exception codes

Code	Name	Description
01	Illegal function	The requested command is invalid.
02	Illegal address	This code indicates one of the following: The requested address is invalid for that function. The requested address is not within the valid register range for this device. The requested address is protected by device security.
03	Illegal value	This code indicates one of the following: The requested value is not allowed for that register in the device. The requested register is part of a multi-word value.

Code

Name

Description

Illegal function

The requested command is invalid.

Illegal address

This code indicates one of the following:

The requested address is invalid for that function.
The requested address is not within the valid register range for this device.
The requested address is protected by device security.

Illegal value

This code indicates one of the following:

The requested value is not allowed for that register in the device.
The requested register is part of a multi-word value.

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.