9410 series
Communications
Modbus commands
A Modbus master command to unit ID 0 is broadcast (sent to) all Modbus slave
devices. The only supported broadcast command is preset multiple registers.
For serial Modbus networks with only one slave device, the master can send
commands using the single connection, one-to-one address of unit ID 248, regardless
of the slave device’s actual unit ID.
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.
Modbus invalid read registers responses
Invalid type
Read response
Unmapped (unused)
1
register
0x8000
Reserved
1
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 does not respond. No data is written or stored, and
the meter does 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.
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7EN05-0336-01