GW-7228 J1939/Modbus RTU Slave Gateway
User’s Manual (Ver 1.3, Apr/2011) ------------- 30
4. Communication Network
4.1 Modbus Network
The GW-7228, J1939 to Modbus Interface, supports the Modbus
RTU serial protocol. It plays a Modbus slave on the network.
4.1.1
Supported Modbus Functions
The Modbus function codes supported by the Modbus interface are
shown as the table below.
Table 4-1 Supported Modbus Function Codes
Function
Code
Function Name
Description
3
(
03
Hex)
Reading Holding
Register
Read multiple registers (4xxxx) for
AO
4
(
04
Hex)
Reading Input
Register
Read multiple input registers (3xxxx)
for AI
6
(
06
Hex)
Preset Single
Register
Write single register (4xxxx) for AO
16
(
10
Hex)
Preset Multiple
Registers
Write multiple registers (4xxxx) for
AO
4.1.2
Modbus Address
Only the areas of the Modbus I/O tables that are configured with
J1939 I/O data are addressable, Modbus functions that use Word
addressing address the I/O tables by using 16-bit words.
