Moeller ps4-201-mm1 - Page 77

Optimizing the exchange of
send and receive data
73
04/99 AWB 27-1184 GB
Figure 27: Subdivision of the COB with incorrect station
address assignment
Sequence of communication:
1. Master sends 40 bytes to slave A:
Free COB memory at this stage = 50 bytes
2. Master receives 50 bytes from slave A:
Free COB memory at this stage = 0 bytes
3. Master sends 30 bytes to slave B:
Free COB memory at this stage = 30 bytes
4. Master receives 40 bytes from slave B:
Overlapping of 10 bytes between send and
receive data. The controller goes to the “Not
Ready” state.
A
B
C
10
40
30
48
A
B
C
50
40
38
욾
128
128
free
Send
Receive
Byte
Byte
욾

The Sucosoft S 40 software automatically
checks the configuration and warns about
possible overlapping.