Rockwell Automation 2706 DL20 SERIES G USER MANUAL - Manual (Page 168)

Appendix G
Application Notes
G–16
SCAN RATE: (4 for PLC-2/PLC-5 example)
If TIME DRIVEN mode was selected previously, then the value entered
represents the period between samplings of the parallel port. The value
entered is in units of 1.95 milliseconds.
Example: 28 = 28 x 1.95 = 54.6 milliseconds between samplings.
Important: You must be sure that data (each step) is present on the parallel
port for at least the scan rate.
If a Parallel Input Converter (Catalog No. 2706-NG1 or -NG2 Series A or B
is used, the SCAN RATE range is 28 - 255 (54.6 - 500 ms). If not, the range
is 4 - 255 (7.8 ms - 500 ms).
DEBOUNCE TIME: (1 for PLC-2/PLC-5 example)
Not applicable for applications using Parallel Input Converters (Catalog No.
2706-NG1, -NG2 Series A or B).
The debounce time is in units of 1.95 milliseconds. The range is 1 - 255.
Debounce time determines how many samples are evaluated during the
sampling period as determined by the scan rate selected. For example, if a
debounce time of 5 is selected, then 5 samples are taken 1.95 milliseconds
apart. All of these samples must match for the data to be read by the DL20.
The debounce time should be at least 3 less than the scan rate.
For AC parallel interface applications using Parallel Input Converters
(Catalog No. 2706-NG1, -NG2 Series A or B), data should be present (each
step of sequencer) at the parallel port for at least 180 milliseconds.
For DC parallel interface applications, data should be present (each step of
sequencer) for at least 20 milliseconds. These are the minimum allowed
values for the sequencer step timer (031 in the PLC -2 example or T4:1 in the
PLC-5 example).
To determine update time, multiply the time interval between sequencer steps
by the number of sequencer steps. In the PLC-2 variable data example, timer
031 in rung 2 determines the time interval between steps. For a setting of
PR010 (100 milliseconds), the update time for the variable data in this
example of 8 steps, will be 800 milliseconds (100 ms x 8).
DL20 Parallel Port
Configuration
Variable Data
Update Times