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5 PLC
5.1.2 Standard functions
5.1.2
Standard functions
Standard functions are only processed in one PLC. The corresponding PLC is activated via a
machine data.
On input by the computer link basic software, standard function message frames are copied by
the MPR into the DB 34 input buffer (figure "Transfer of standard message frames").
Decoding and processing of the message frame are done subsequently by the STEP 5
standard function blocks.
The processing result is entered as a signal in the standard area of the user interface for the
input (DB 101, DW 0 to 15).
All other PLCs which do not process the standard functions must retrieve the information from
the buffer for the standard signals in the MPR and copy them into their standard interfaces for
input.
Output to the production control computer from the user interface standard area is only
possible by the PLC which is determined by machine data for processing of the standard
message frames.
The output from the standard interface can take place on initiative of the user (action) or as
response of the user to the production control computer's initiative.
For the output, the message frame and addressing data are processed due to a signal in the
standard output interface in DB 102. Then this block is entered by the STEP5 standard
function blocks into the output buffer DB 35. The OS part of the PLC-CL basic software
transfers the message frame from the output buffer for the STEP 5 standard function blocks
into a PLC output buffer (in the MPR).
COM
MPR
O
I
O
I
I
O
I
O
Transfer of standard message frames
5–6
PLC
Buffer
input
DB 34
PLC
OS
Buffer
output
DB 35
© Siemens AG 1989 All Rights Reserved
DB 101
Std.sig.
input
STEP 5
standard
routines
DB102
Std.sig.
output
6FC5 197-0AB20-0BP0
SINUMERIK 840/880 (PJ)
08.89
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