Message Formats; Command Format - Omron V780 Series User Manual

7-2

Message Formats

7-2-1

Command Format

Byte-0 Byte-1 Byte-2
Transaction iden-
Protocol identifier
tifier
XXXX hex Always 0000 hex.
X: Any value, n: 4,351 max.
Transaction Identifier
This value is used to identify the message sent by the host device.
The transaction identifier in the response from the Reader/Writer will be a copy of the value that is
specified here.
Protocol Identifier
This field is always 0000 hex.
Field Length
Specify the number of bytes inclusively from the unit identifier through the end of the data.
If the function code is FC03 or FC16, the maximum field length is 250 bytes.
If the function code is FC100, the maximum field length is 4,346 bytes.
Unit Identifier
This field is always FF hex.
Function Code
The function code indicates the command to request execution from the Reader/Writer.
Function code
FC03 (03 hex)
FC16 (10 hex)
FC100 (64 hex)
UHF RFID System V780-series Reader/Writer User's Manual (Z389)
Byte-3 Byte-4 Byte-5
Field length
XXXX hex
Command frame length
Function
Read Multiple Registers
Write Multiple Registers
Reader/Writer command
7 Modbus/TCP Communications
Byte-6 Byte-7 Byte-8
Func-
Unit
tion
identifier
code
03 hex,
Always 10 hex,
FF hex. or 64
hex
Range included in the field length.
Modbus/TCP Class 0 compliant
This function code is used for commands
with a unique manufacturer definition that
gives priority to the performance of commu-
nications with the host device.
Byte-9 ... Byte-n
Data
XX...XX hex
Remarks
7 - 5
7