IME IF2E011 - Bridge Mode with ModBus Over TCP

3
Bridge (Filter) with ModBus Over TCP
The ModBus Over TCP frame, after having been extracted from the IP
message will be :
Incremental
number
hi
Incremental
number
Lo
Protocol
type
Protocol
type
Byte
number
Hi
Byte
number
Lo
Node
address
Function
code
Regist
er Hi
Register
Lo
Length
Hi
Length
Lo
00
01
00
00
00
06
01
03
10
00
00
02
The interface performs some operations to get the original message.
Node
Address
Function
code
Register
Hi
Register
Lo
Length
Hi
Length
Lo
CRC16
Lo
CRC16
Hi
01
03
10
00
00
02
C0
CB
Answer from the slave n. 1
Node
Address
Function
code
Bytes
number
Value 1
Hi
(MSW)
Value 1
Lo
(LSW)
Value 2
Hi
(MSW)
Value 2
Lo
(LSW)
CRC16
Lo
CRC16
Hi
01
03
04
00
00
00
00
FA
33
The interface, after having received the answer message, will perform the
mirror operation :
Increme
_ntal
number
hi
Increme
ntal
number
Lo
Protocol
type
Protocol
type
Byte
number
Hi
Byte
number
Lo
Node
address
Function
code
Byte
number
Value 1
Hi
(MSW)
Value 1
Lo
(LSW)
Value 2
Hi
(MSW)
Value 2
Lo
(LSW)
00
01
00
00
00
07
01
03
04
00
00
00
00
In this mode, the interface works as a protocol converter so allowing the
interfacing with devices not capable to understand the Modbus Over TCP