Fieldbus controller 750-842 • 63
Process data architecture for MODBUS/TCP
Modular I/O System
ETHERNET TCP/IP
Address
Bytes
Comment
Module
Offset
High
Low
0
C/S
Control / Status byte
1
D1
D0
ead/set counter word
3
(D2)*
)
(period)
4
D4
D3
read latch word
Module 1:
750-631,
750-631/000-001
5
User data
User data
Data bytes
Module 2:
Analog module Channel 1
6
User data
User data
Data bytes
Module 2:
Analog module Channel 2
...
...
...
...
...
The control / status byte is in the low byte on offset 0.
The data word D0/D1 contains the counter word (read/set), whereas the data
word D3/D4 contains the latch word (read).
*
)
In the operating mode of permanent period measurement, the period dura-
tion is in D2 together with D3/D4.
3.2.4.3.6 750-650 RS232 Interface module,
750-651 TTY-,20 mA Current Loop,
750-653 RS485 Interface module
This process data architecture holds true for the modules 750-650, 750-651
and 750–653.
Item-No.:
Description:
750-650
RS 232 C Interface 9600,n,8,1
750-651
TTY Interface, 20 mA Current Loop
750-653
RS485 Interface
The modules appear on the bus as a combined analog input and output module
with 3 x 16-bit input and output data, i.e. with a total of 4 bytes user data. Here
2 words each are occupied with word-alignment.
Address
Bytes
Comment
Module
Offset
High
Low
0
D0
C/S
Data
byte
Control /
Status byte
1
D2
D1
Data bytes
Module 1:
750-650,
750-651,
750-653
2
User data
User data
Data bytes
Module 2:
Analog module Channel 1
3
User data
User data
Data bytes
Module 2:
Analog module Channel 2
...
...
...
...
...
