Configuring Hardware and Communication Connections STEP 7.pdf

Configuring the Distributed I/O (DP)
Process Reaction Times with Constant Bus Cycle Time and Clock
Synchronization
SIMATIC produces reproducible (that is, repeatable, of equal length) reaction times
by means of a constant (isochrone) DP bus cycle and synchronization of the
individual cycles previously listed.
In this case, the situation corresponds to the example given above with the
difference that all cycles (up to the OB 1 cycle) are of equal length and
synchronously cycled. The clock pulse generator is comprised of the DP master
constant bus cycle time clock that is sent as the global control frame to the DP
slaves. A synchronous cycle interrupt OB 61 (or OB 61 to OB 64) ensures that it
is synchronized with the user program.
Configuring Hardware and Communication Connections with STEP 7
3-84 A5E00706939-01