AutomationDirect DL105, User Manual

Page: 98 / 350

High
-S
peed
Input
and
Pulse
O
utput
Features
3--22
High-speed Input and Pulse Output Features
DL105 PLC User Manual, 3rd Edition
X4
RST
When the preload request is made, the user turns
on X4. First we disable counting by resetting C0,
the counter’s enable input.
C0
PD
Generate a preload counter input pulse, which
causes the counter to preload from V1076-V1077.
C1
LDD
K3000
Load the BCD value K3000 into the
accumulator.
OUTD
V1076
Output the constant to V1076/V1077, the location
of the accumulated pulse count.
Preload counter
C1 C0
SET
C0
Enable the counter by setting C0, when the
preolad pulse on C1 has occurred (C1 is off).
If you’re having trouble with Mode 20 operation, please study the following
symptoms and possible causes. The most common problems are listed below.
Symptom: The counter does not count.
Possible causes:
1.
Field sensor and wiring
-- Verify that the encoder or other field device
inputs actually turn on and illuminates the status LEDs for X0 and X1. A
standard incremental encoder will visibly, alternately turn on the LEDs for
X0 and X1 when rotating slowly (1 RPM). Or, the problem could be due to a
sinking-sourcing wiring problem, etc. Remember to check the signal
ground connection. Also verify that the pulse on-time, duty cycle, voltage
level, and frequency are within the input specifications.
2. Configuration -- make sure all of the configuration parameters are correct.
V7633 must be set to 20, and V7634 must be set to “0012” to enable the
Phase A input, and V7635 must be set to “0000” to enable the Phase B
input.
3. Stuck in reset -- check the input status of the reset input, X2. If X2 is on, the
counter will not count because it is being held in reset.
4. Ladder program -- make sure you are using counter CT76 in your
program. The top input is the enable signal for the counter. It must be on
before the counter will count. The middle input is the preload input and must
be off for the counter to count. The bottom input is the counter reset, and
must be off during counting.
Symptom: The counter counts in the wrong direction (up instead of down, and visa-versa).
Possible causes:
1. Channel A and B assignment -- It’s possible that Channel A and B
assignments of the encoder wires is backwards from the desired
rotation/counting orientation. Just swap the X0 and X1 inputs, and the
counting direction will be reversed.
Symptom: The counter counts up and down but will not reset.
Possible causes:
1. Check the LED status indicator for X2 to make sure it is active when you
want a reset. Also verify the configuration register V7636 for X2 is set to 7.
Or, if you are using an internal reset, use the status mode of Direct SOFT to
monitor the reset input to the counter.
Counter Preload
Program Example
Troubleshooting
Guide for Mode 20