Allen-Bradley A-B QUALITY DL20 Series User Manual page 166

Appendix G
Application Notes
PLC-5 Programming
Examples
G–14
Rung Descriptions (Figure G.4)
Rung 2:0
Each time input T4:0/dn is true, the sequencer output instruction outputs
the next step. The sequencer done bit is set when the sequencer reaches
rung 2:4. The sequencer then resets itself and begins again.
Rung 2:1
Timer T4:0 is a free running timer which drives the SQO. A preset value
of 3 provides a pulse every 30 msec.
Rung 2:2
Timer T4:1 is a free running timer which generates the variable data for
the DL20.
Rung 2:3
Masks off the low byte data from T4:1.ACC and moves it to lower byte of
N7:9. The low byte data is now in a format that can be output to the
DL20 data lines (D0 through D7).
Rung 2:4
Transfers or distributes the high byte of T4:1.ACC to the lower byte of
N7:10. The high byte data is now in a format that can be output to the
DL20 data lines (D0 through D7).
Rung 2:5
Takes the high byte data at N7:10 and moves it to N7:2 for use with the
SQO. The upper byte of N7:2 is preloaded with the correct bit pattern to
control the strobe lines using the Data Monitor. This has the effect of a
logic OR for the changing high byte variable data and the constant strobe
bit settings.
Rung 2:6
Takes the low byte data at N7:9 and moves it to N7:3 for use with the
SQO. The upper byte of N7:3 is preloaded with the correct bit pattern to
control the strobe lines using the Data Monitor. This has the effect of a
logic OR for the changing low byte variable data and the constant strobe
bit settings.