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11 Data Transfer PLC/NC/COM (DB 36)
11.2 Data transfer PLC/Initiative
11.2
Data transfer PLC/Initiative
11.2.1 Structure and signal path
Data can be exchanged between the PLC and NC or COM via data channels. If two PLCs are
installed, data transfer can be initiated by either of them.
2 function blocks for activating the transfer of data are available in the PLC operating system:
read NC data (FB 61) and write NC data (FB 62) (see description of function macros).
The following figure shows the structure of data transfer on PLC initiative.
Structure of data transfer on PLC initiative: in this case, reading NC data
FB 61
READ NC DATA
Link
RAM
PLC
operating
system
Data
channel
NC/PLC
PLC
initiative
PLC user
program
a a a a a a a a a a a
a a a a a a a a a a a
a a a a a a a a a a a
a a a a a a a a a a a
a a a a a a a a a a a
a a a a a a a a a a a
FIFO
jobs
DB 36
Status
data
transfer
DB n
Data
LESE
NSBY
ANZ
DTY
WER
ZFPN
ZIEL
The function blocks enter the parameters for data transfer (data type, data source, data
destination) in an internal interface. The interface is a first-in first-out (FIFO) register with a
maximum capacity of 8 jobs. Even when several jobs are involved, this ensures that they are
executed in the correct sequence.
Each job must still be allocated an interface byte indicating the status of data transfer (DB 36,
DW 0 ... DL 32 corresponds to 65 interface bytes). Data transfer can be checked and
branches implemented in the user program according to these acknowledgements
.
© Siemens AG 1991 All Rights Reserved 6ZB5 410-0HE02
11–3
SINUMERIK 880 (PJ)