I/O Terminal /
MANUAL CONFIGURATION
36
Byte 9, bit 4
Byte 9, bit 6
Byte 12, bit 0
Byte 12, bit 1
Standard-Bus mode
0
bin
1
bin
0
bin
0
bin
Slow FreeRun
1
bin
1
bin
0
bin
0
bin
Fast
FreeRun
0
bin
0
bin
0
bin
0
bin
Synchronous
0
bin
0
bin
1
bin
0
bin
Synchronous
with
optimized input
update, one cycle
0
bin
0
bin
0
bin
1
bin
Synchronous with
optimized input
update, two cycles
FreeRun Mode
This section covers the types of FreeRun Modes.
Slow FreeRun(default setting)
In the FreeRun mode there is no synchronization between the Standard-Bus cycle and the
DP cycle. It is a characteristic feature of the Slow FreeRun mode that the Standard-Bus cycle
is called from the main task. Acyclic communication or events result in heavy jitter in the
Standard-Bus cycle (DPV1, terminal diagnosis, etc.), because all of these functions are also
called from the main task.
Fast FreeRun
To avoid the jitter resulting from acyclic communication or events and to achieve fast
Standard-Bus update times, the Fast FreeRun mode can be activated. The Standard-Bus
cycle is called under time control from a high priority task. Following completion of the
Standard-Bus cycle, the lower priority tasks (DPV1 etc.) are granted processor time for
12.5% of the duration of the foregoing Standard-Bus cycle, before the next Standard-Bus
cycle is started. In fast FreeRun mode therefore the inputs and outputs are tightly up-to-date,
but are not synchronized to the DP cycle:
