QUESTION:
How often can I call the system function SFC12 "D_ACT_DP" at the same time?

ANSWER:
SFC12 "D_ACT_DP" works asynchronously, i.e. this system function executes a task spanning over several cycles. In order to enable the execution of all necessary cycles, the parameter "REQ" has to be set as long as the task is active. The parameter "REQ" needs to stay on "TRUE", until the parameter "BUSY" has reached the "FALSE" level again.

using the S7 300 CPUs with an internal DP interface; the SFC12 can be called up to four times at the same time. The SFC12 can be called up to four times per DP rope (internal and external) at the same time at the S7-400 CPUs.

Note:
When using the CP342-5 as a DP master, SFC12 cannot be used for the activation/deactivation.

Activating a DP-Slave might be costly in time. If you want to abandon a running activation order, start the system function with the same value for LADDR and MODE = 2. Repeat the call with MODE = 2 till the successful abort of the activation task is displayed with RET_VAL. This procedure is only possible with the CPUs of the S7-300 line. You cannot abandon the task with S7 400 CPUs.

Note:
More information about the SFC12 can be found in the manual "SIMATIC System software for S7-300/400 System and Standard functions" at EntryID: 1214574" and in the STEP 7 ONLINE Help (Mark SFC block in the block container and press the F1 key).