Siemens SIMATIC S5 Manual page 133

Data Transmission Using Cyclic I/O
Status Byte for the ZP Slave:
Error codes Status codes
7 6 5 4 3
R R R R
R: Read only
Irrelevant bit (=0)
Figure 7-7. Structure of the Status Byte (STB) for the ZP Slave
7-10
2 1 0
R R R
0: No ZPE cycle overflow
1: ZPE cycle overflow:
New ZP input data are available in ZP DB from ZP master
although the CPU could not yet take over previous ZP input data.
0: No ZPA cycle overflow
1: ZPA cycle overflow:
The CPU has provided new ZP output data from the ZP DB to
the communications processor although previous ZP output data
could not yet be preprocessed for the bus.
0: The ZP master transmitted the programmed number of ZP input
data.
1: The ZP master did not transmit the programmed number of ZP
input data:
- If too many data were sent, the rest is discarded.
- If too few data were sent, the rest is filled up with "0".
0: ZP bus cycle is presently running.
1: A ZP bus cycle ended at the last ZP control point (before this
OB1 cycle) (scanning of the ZP slave by the ZP master):
- The newest ZP input data are available from the ZP master.
Bit 3 stays set for one PLC-CPU program cycle.
0: ZP data in ZP DB are valid.
1: ZP data in ZP DB are temporarily invalid; previous ZP output
data are being transmitted via the bus.
0: No ZP DB error
1: Programmed ZP DB is not available or ZP DB is too small; ZP
image in ZP DB is invalid, ZP output data "0" are transmitted via
the bus.
0: The ZP master is okay.
1: The ZP master has failed, is still in the start-up phase (ZP slave
was not scanned within a certain "access time") or the ZP slave
is still in the start-up phase; the complete ZPE in ZP DB is set to
"0".
S5-95U, SINEC L2
EWA 4NEB 812 6112-02