Technical data

11.5 Updating the Input and Output Areas with the DP
Service
Depending on the selected mode, the CP distinguishes between two times
when the DP output bytes for transmission can be accepted:
➣
FREE mode: decided by the CP (the STEP 5 control program has no
influence)
➣
CYCLE-SYNCHRONIZED mode: decided by the control program using
a send handling block call with job number 210.
Depending on the selected mode, the CP distinguishes between two times
when the DP input bytes
received
can be transferred:
➣
FREE mode: decided by the CP (not influenced by the STEP 5 control
program)
➣
CYCLE-SYNCHRONIZED mode: decided by the control program using
a RECEIVE handling block call with job number 211.
11.5.1 Consistency of the Input and Output Bytes with the DP
Service of the CP
The consistency of the DP I/O bytes depends on the selected mode.
➣
FREE mode: guaranteed consistency of only one byte for the I/O DP
area.
➣
CYCLE-SYNCHRONIZED mode: The data of the whole I/O DP area is
consistent. Whenever you want to work with consistent I/O areas, for
example, when using the analog I/Os in the ET200U, you must select
the CYCLE-SYNCHRONIZED mode.
B8976060/02 Distributed I/Os (DP)
11 - 11 Volume 1