Siemens SIMATIC S5 Manual page 166

Data Transmission by Accessing Layer 2 Services
8.8 Holding Data Ready for Fetching Several Times Over by One or More
Stations (RUP_MULTIPLE Service)
The RUP_MULTIPLE (Reply UPdate MULTIPLE) service is used for holding data for fetching in an
active or passive station. The data held can be fetched by an active station several times over,
using the SRD service ( section 8.9) ; from either one or several active stations.
Before the sender requests data from the receiver (SRD layer 2 service), the receiver must keep
the data ready in an SAP.
The receiver uses either the RUP_SINGLE or RUP_MULTIPLE service to do this ( section 8.8).
The RUP_MULTIPLE service ensures that the SAP keeps the requested data ready for fetching
until the SAP is overwritten by a new RUP_SINGLE or RUP_MULTIPLE . The data in the SAP
can therefore be read out several times.
If only one station is to fetch the data, this is also possible with the RUP_MULTIPLE service, but is
better done with the RUP_SINGLE service.( section 8.7).
Reason: If the RUP_MULTIPLE service is used, the sender cannot distinguish between new data
and data that have already been requested.
Data holding procedure for the receiver ( Figure 8.12):
The request (header + net data to be held ready for fetching) in the flag or data area is sent
with L2-SEND (request to layer 2).
The 'Send' status byte informs the receiver that a confirmation has been transmitted, and the
receiver fetches the confirmation (= header) with L2-RECEIVE.
S5-95U
Sender control program (Station 1 in the
The data are fetched by the
sender with the SRD service.
The receiver then gets an
indication, which it must fetch
with the L2-RECEIVE
( Section 8.9).
Figure 8-12. Holding Data Ready for Fetching with the RUP_MULTIPLE Service
Since the receiver sends data to itself with the RUP_MULTIPLE service, you must specify the
same SAP in DB1 for sending and receiving ( section 8.3). The destination SAP in the request
header is irrelevant.
8-26
LAN bus
Receiver control program (Station 2 in the
example)
SAP
Request
(Data)
Confirmation
RECEIVE
STBS:...4
S5-95U, SINEC L2
S5-95U
SEND
Request header
8 bytes
RUP_MULT.
ID: 07
H
STBS:...2
In example: DB33,
H
DW 1 to DW 4
STBS:...3
Data
H
In example: DB33,
DW 5 to DW 8
Confirmation
header, 8 bytes
In example: DB33,
H
DW 10 to DW 13
EWA 4NEB 812 6112-02