Fig. 42 K-Bus - Synchronous Mode With Optimized Input Update (One Cycle); Fig. 43 K-Bus - Synchronous Mode With Optimized Input Update (Two Cycles) - Beckhoff BK3 0 Series Documentation

Fig. 42: K-bus - synchronous mode with optimized input update (one cycle)
The delay time is set by means of the UserPrmData [} 35] (in µs, in Motorola format). The extended GSD file
of the Bus Coupler is, however, necessary for this:
Byte
13
14
Synchronous mode with optimized input update (two cycles)
In the third mode of synchronous operation, the advantages of the other two operating modes are combined.
Two K-bus cycles are carried out within one DP cycle. The first cycle begins immediately after reception of
the Data_Exchange telegram from the master, which means that the outputs are generated as quickly as
possible. The second cycle is started after a delay time that begins after completion of the first cycle has
elapsed, so that the inputs are as recent as possible. It is important here to ensure that two times the
duration of the K-bus cycle, plus the delay time, plus approx. 20 % (to allow for the lower priority processes
on the coupler) is shorter than the DP cycle time (which, under TwinCAT, means the cycle time of the
associated task).
Fig. 43: K-bus - synchronous mode with optimized input update (two cycles)
The delay time is set by means of the UserPrmData [} 35] (in µs, in Motorola format). The extended GSD file
of the Bus Coupler is, however, necessary for this:
Byte
13
14
Dummy output byte
The Bus Coupler's PROFIBUS DP ASIC can only generate an interrupt after reception of a Data_Exchange
telegram if output data has been received. This means that at least one output byte must be transferred via
DP in synchronous mode. If only input terminals are plugged in, and no output data is therefore present, a
dummy output byte can be configured. It is activated in the UserPrmData [} 35], and must be entered as the
module in the CfgData. The extended GSD file for the Bus Coupler is, however, necessary for this:
BK3xx0
Value: Description
Delay time (in µs) high byte
Delay time (in µs) low byte
Description
Delay time (in µs) high byte
Delay time (in µs) low byte
Version: 4.3.0
PROFIBUS DP communication
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