01.93
11 Data Transfer PLC/NC/COM (DB 36)
11.3 Data transfer NC initiative
11.3
Data transfer NC initiative
On the SINUMERIK 880, PLC data can be read/written directly by the NC and COM CPU. The
NC or COM requests or supplies data via an interface; data transfer takes place via the PLC
operating system.
PLC data for the NC CPU can be read and written using commands in the cycle language
CL 800.
Appropriate commands are available for data types I, Q, F, T, C and D (see CL 800
documentation).
Data from the PLC are written in R parameters by the CL 800 command; data to the PLC must
be entered in an R parameter before calling the CL 800 command.
This function permits data to be exchanged between the PLC and NC cycles without a PLC
user program; the user merely has to reserve certain data storage areas (e.g. a data block) in
the PLC for data transfer purposes.
Note:
In the event of major data storage areas being altered in the PLC by an NC program, users are
recommended to set a strobe bit in the PLC after completing the data transfer. This obviates
the need for time-consuming comparisons of data fields to identify alterations. Certain bits can
be set in the PLC as strobes via CL 800; M functions can also be used to identify data altera-
tions.
11.4
Data transfer COM initiative (available soon)
PLC-COM transfer on COM initiative is required in cases where display programs have to be
supplied with PLC data. The displays have to be compiled with the NC programming terminal
and stored in the EPROM in the COM area. When compiling displays with the NC programm-
ing terminal, the exact data source in the PLC (I, Q, F, T, C, D) has to be stated for each vari-
able.
When a display with PLC variables is selected at the NC, the display program requests the
content of the PLC variables from the PLC operating system, carries out any necessary format
conversions and then displays the variables.
If PLC data are to be written after an input at the NC operator panel keyboard, the same
procedure is followed in the reverse sequence.
No additional function blocks are required in the PLC for obtaining displays with PLC variables;
all functions needed to obtain the display are contained in the NC display program or PLC
operating system.
Exception:
Function blocks from FB package 0 are required to display and interrogate PLC messages.
© Siemens AG 1991 All Rights Reserved 6ZB5 410-0HE02
11–11
SINUMERIK 880 (PJ)
