Siemens MICROMASTER 440 Operating Instructions Manual page 194

3 Functions
The free function blocks (FFB) are enabled in two steps :
1. General enable P2800:
The function "Free function blocks (FFB)" is enabled using parameter P2800
(P2800 =1).
2. Specific enable P2801, P2802:
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.
All free function blocks are called within the 128 ms time slice (cycle time). Further,
to adapt to the application, the chronological sequence in which the FFB are
executed, can also be controlled. This is especially important so that the FFB 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 following Table indicates that the priority decreases from the top towards the
bottom (priority 1 → level) or from the right to left (priority 2 → line) (refer to Table
3-32).
Table 3-32
Level 3
Level 2
Level 1
Inactive 0
Example 1:
Enabling the FFB:
Enabling individual FFB including assigning a priority:
P2801[0] = 1
P2801[1] = 2
P2801[2] = 3
P2802[12] = 2
P2802[13] = 3
The FFB are calculated in the following sequence:
AND 3, CMP2, AND 2, CMP 1, AND 1
194
FFB priority table
P2800 = 1
AND 1
AND 2
AND 3
CMP 1
CMP 2
low
MICROMASTER 440 Operating Instructions
6SE6400-5AW00-0BP0
Issue 10/06
Priority 2
high