Diagnostics And Interrupt Functions - Siemens SIMATIC ET 200AL System Manual

Functions
5.1 Isochronous mode
Programming isochronous mode
To operate your plant in isochronous mode, the user program must be structured
accordingly. This means you have to add a synchronous cycle interrupt in the STEP 7
project tree.
You access the isochronous I/O by means of a process image partition, which means the
addresses of the isochronous modules must be located in a process image partition. You
program access to isochronous I/O with the "SYNC_PI" instructions (updating the process
image partitions of the inputs) and "SYNC_PO" (updating the process image partition of the
outputs) in the synchronous cycle interrupt OB.
You call the "SYNC_PI" instruction at the start of the synchronous cycle interrupt OB,
provided you have selected the automatic setting for the delay time. You call the
"SYNC_PO" instruction at the end of the synchronous cycle interrupt OB.
5.1.7

Diagnostics and interrupt functions

The diagnostic and interrupt functions of STEP 7 are available for isochronous mode. These
reduce downtimes and simplify localization and elimination of faults.
Events, causes of errors and remedies
Below, you will find the events for diagnostic and interrupt functions and remedies for the
problem.
Table 5- 1 Events, causes of errors and remedies
Event
Synchronous cycle interrupt OB is
•
started with the input parameter
EventCount > 0 (number of lost OB
calls since last OB call)
If configured:
Call of the time error OB
•
Diagnostic buffer entry "Buffer overflow
•
for OB6x events"
Error (negative RetVals) when updating
the isochronous process image partition
with SYNC_PI / SYNC_PO:
Consistency warning
•
Update time is after / before the
•
permitted access window.
Error when updating the isochronous
process image partition with
SYNC_PI / SYNC_PO:
Access error
•
70
Cause of the error
The synchronous cycle interrupt OB
takes too long.
SYNC_PI / SYNC_PO are not called
in the permitted access window in
the synchronous cycle interrupt OB,
which means they are called or
processed during the I/O data
transfer on PROFIBUS.
DP slave / module does not respond
/ is not available.
Remedy
Shorten the synchronous cycle
•
interrupt OB.
Increase the DP cycle.
•
Reduce the delay time setting
•
(setting with isochronous mode at
synchronous cycle interrupt OB).
Increase the delay time.
•
Increase the DP cycle.
•
Adapt the program.
•
PROFIBUS with STEP 7 V13
Function Manual, 12/2014, A5E03775446-AC