Event-Only Transitions; Counter Assignments - Automation Direct DL05 User Manual

Chapter 6: Drum Instruction Programming

Event-Only Transitions

1
Step transitions do not require both the event and the timer criteria programmed for each
step. You have the option of programming just one of the two, and even mixing transition
2
types among all the steps of the drum. For example, you might want Step 1 to transition on
an event, Step 2 to transition on time only, and Step 3 to transition on both time and an
event. Furthermore, you may elect to use only part of the 16 steps, and only part of the 16
3
outputs.
4
5
6
7
8
9

Counter Assignments

Each drum instruction uses the resources of four counters in the CPU. When programming
10
the drum instruction, you select the first counter number. The drum also uses the next three
counters automatically. The counter bit associated with the first counter turns on when the
11
drum has completed its cycle, going off when the drum is reset. These counter values and the
counter bit precisely indicate the progress of the drum instruction, and can be monitored by
your ladder program.
12
Suppose we program a timer drum to have 8
steps, and we select CT10 for the counter number
13
(remember, counter numbering is in octal).
Counter usage is shown to the right. The right
14 column holds typical values, interpreted below.
CT10 shows that we are at the 1528th count in the current step, which is step 4 (shown in
CT13). If we have programmed step 4 to have 3000 counts, then the step is just over half
A
completed. CT11 is the count timer, shown in units of 0.01 seconds. So, each least-
significant-digit change represents 0.01 seconds. The value of 200 means that we have been in
B
the current count (1528) for 2 seconds (0.01 x 100). Finally, CT12 holds the preset step value
which was programmed into the drum instruction. When the drum's Reset input is active, it
presets to step 1 in this case. The value of CT12 changes only if the ladder program writes to
C
it, or the drum instruction is edited and the program is restarted. Counter bit CT10 turns on
when the drum cycle is complete, and turns off when the drum is reset.
D
6–6
DL05 Micro PLC User Manual, 6th Edition, Rev. A
Step 1 Outputs:
No
Is Step event
true?
Yes
Step 2 Outputs:
Use next transition criteria
Counter Assignments
CT10
Counts in step V1010
CT11
Timer Value
CT12
Preset Step
CT13
Current Step
1528
V1011 0200
V1012 0001
V1013 0004