User's Manual

COBALT UHF-SERIES CHAPTER 7: MODBUS TCP INTERFACE
PAGE 115 OF 140
7.2.2 Modbus TCP - Command Packet Structure
Consume Registers hold data that is destined for the Cobalt. Modbus TCP
commands must be placed in the holding registers, starting at address 40001, of
Device ID 01 (Node Input Page 01). Commands utilize at least six registers (double-
byte values or words).
MODBUS
ADDRESS
(4XXXX /
3XXXX)
READ / WRITE
PRIVILEGE
REGISTER DESCRIPTION
(40001) 1
R/W 2-byte Consume Data Overall Length
(> 0 indicates data is available; Cobalt clears to 0
after data is processed)
2
R/W MSB = Reader Type
LSB = Command ID
3
R/W MSB = 0x00
LSB = Node ID (0x01 for the Cobalt)
4
R/W 2-byte Timeout Value
(0-65535) measured in milliseconds
5
R/W 2-byte Start Address
(0-65535)
6
R/W 2-byte Read/Block Size
(0-65535 bytes)
7 – 32774
R/W Cobalt Consume Data (when applicable)
32775 – 65536
R/W Reserved
Table 7-1: Modbus TCP - Command Packet Structure