Allen-Bradley 1756-OB16IS - Page 6

Rockwell Automation Publication 1756-AT017A-EN-P - January 2013
6 Position-based Output Control with the MAOC Instruction
Figure 2 shows an example of the 1756-OB16IS module processing eight
schedules in the normal order (illustrated alphabetically). The module processes
the last schedule on output 0, then the last schedule on output 1, followed by the
last schedule on output 2, and so on. The module then processes the second to
last output for each output point. After the module processes the last schedule,
the processing completes. Any unprocessed schedules are not acted upon.
In the figure, the dashed lines signify the intended behavior, and the solid lines
show the actual behavior for these schedules:
•G—The schedule is processed; however, there is no change of state because
of the previous state of the output.
•H—The schedule turns output 1 Off, but much later than expected.
•I—This transition and all of the unmarked transitions are never processed.
If the 1756-OB16IS module in this example is replaced with a 1756-OB16IEFS
module with a higher schedule count, all of the schedules can be processed and
executed. Slowing down the master axis can also help because fewer schedules are
executed within each CUP.
Figure 2 - Schedule Limitations
Schedules Per CUP for 1756-OB16IS = 8
Next CUP
Current CUP
Previous CUP
On
Off
On
Off
Output 0
Output 1
On
Off
Output 2
G
D
A
D
I
H
E B
F C