QUESTION:
What are the options for communications via MPI?
ANSWER:
The following protocols are possible on the MPI bus:
- S7 basic communication
- S7 communication
- Global data communication
- PG/OP communication
Multiple utilities are available for these protocols with
different parameters:
- S7 basic communication
| S7 basic
communication |
SFC65 "X_SEND" /
SFC66 "X_RECV" |
SFC68 "X_PUT" /
SFC67 "X_GET" |
| Max. data length |
76 bytes |
84 bytes (S7-400)
76 bytes (S7-300) |
| Configuration type |
Not configured |
Not configured |
| Connection type |
Dynamic client/client
connection |
Dynamic/static client/server
connection |
Sample application
(Entry ID) |
20989875 |
- |
Table 1: S7 basic communication
- S7 communication
(table does not apply for S7-300, because an S7-300 CPU can only
be used as service in S7 communication via MPI.)
| S7 communication |
SFB8 "USEND" /
SFB9 "URCV" |
SFB12 "BSEND" /
SFB13 "BRCV" |
SFB15 "PUT"/
SFB14 "GET" |
| Max. data length |
160...453 bytes* |
32768...65534 bytes* |
Put: 160...452 bytes*
Get: 160...462 bytes* |
| Configuration type |
Configured on both sides |
Configured on one side |
| Connection type |
Static client/client connection |
Static client/server
connection |
Sample application
(Entry ID) |
- |
20987358 |
- |
* Detailed information on data lengths is available in the
manual "System Software for S7-300/400 System and Standard
Functions" (chapter 19 - S7 Communication - User Data Size) in
Entry ID: 1214574
Table 2: S7 communication
- Global data communication
| Global data
communication |
Values |
| Max. data length |
22 byte (S7-300) /
54 bytes (S7-400)
22 bytes
(S7-300/S7-400) |
| Configuration type |
No configured connection |
| Connection type |
Broadcast (no connection in this
sense) |
Sample application
(Entry ID) |
430498 |
Table 3: Global data communication
For global data communication you can use system functions SFC60
"GD_SND" / SFC61 "GD_RCV" for S7-400.
A master document on communication with SIMATIC S7 is available
in Entry ID: 20982954.
| 
german
