Siemens SINAMICS G120 Operating Instructions Manual page 268

Functions
8.14 Free function blocks
The free function blocks (FFB) are enabled in two steps:
1. General enable P2800:
2. Specific enable P2801, P2802:
All free function blocks are called within the 128 ms time slice (cycle time). Additionally, to
adapt to the application, the chronological sequence in which the FFBs are executed, can
also be controlled. This is especially important so that the FFBs are executed in the
sequence which is technologically correct. Parameter P2801 and P2802 are used for the
individual enable function as well as to define the priority in which the blocks are executed.
The following priority levels can be assigned:
● 0 = Inactive
● 1 = Level 1
● 2 = Level 2
● 3 = Level 3
The figure below indicates that the priority decreases from the top towards the bottom
(priority 1 → level) or from the right to left (priority 2 → line).
Figure 8-49
Example 1
Enabling the FFBs:
Enabling individual FFB including assigning a priority:
P2801[0] = 1
P2801[1] = 2
P2801[2] = 3
P2802[12] = 2
P2802[13] = 3
The FFBs are calculated in the following sequence:
8-72
The function "Free function blocks (FFB)" is enabled using parameter P2800 (P2800 =1).
Using parameter P2801 or P2802, the particular function block is enabled (P2801[x] > 0
or P2802[x] > 0) and the sequence in which they are executed is also defined.
Free function block priorities
P2800 = 1
AND 1
AND 2
AND 3
CMP 1
CMP 2
AND 3 → CMP 2 → AND 2 → CMP 1 → AND 1
Operating Instructions, 11/2006, A5E00766042B AA
Control Units CU240S