Echelon LonPoint Application and Plug-In - Manual (Page 32)

3-6 Digital Input/Counter Functional Block
DRY_CONTACT:
minimum period = min(500ms, 2 * debounce interval)
maximum frequency = 1/minimum period
5V, 12V, 24V, or 32V :
maximum frequency = 20kHz
Repeating Count
Counts the off to on transitions from zero up to a configurable value called the
terminal count. When the Digital Input/Counter reaches the terminal count the
count is reset to zero. For example, a terminal count of 4 would produce values
of zero, one, two, three, zero, one, two, three, … on the Analog output network
variable (an appropriate network variable type for the Analog output network
variable in this mode is SNVT_count_f).
The Digital Input/Counter signals that it has reached the terminal count by
asserting the Digital network variable. The Digital network variable stays
on until the Control network variable is set to CLEAR.
If the hardware input has been configured for Dry Contact, the input may be
configured to be debounced with a configurable time period. If the hardware
input has been configured for voltage input (5V, 12V, 24V, or 31V), debounce is
not supported.
If the Control network variable is not connected, the Repeating Count
processing will free-run and count repeatedly from zero to terminal count –1 on
the Analog network variable. In this case the maximum input frequency is
dependent on input hardware configuration as follows:
DRY_CONTACT:
minimum period = min(500ms, 2 * debounce interval)
maximum frequency = 1/minimum period
5V, 12V, 24V, or 32V :
maximum frequency = 20kHz
If the Control network variable is connected, the Repeating Count maximum
input frequency is dependent on the time between the Digital network variable
going to On and downstream logic setting the Control network variable to
CLEAR
for a short enough time period such that the count function does not reach
the terminal count a second time.
Repeating count example:
A canning application needs to determine when four cans have passed down a
chute to tell a downstream boxing machine to package the cans. The boxing
machine indicates when it has completed its task. On the Digital Input/Counter,
select Repeating Count mode, set the terminal count to four, and the Default
Input for the Control network variable to RUN via the LonPoint Plug-in. After
reset the count is set to 0, as cans go by, the count reported by the Analog
network variable goes; 0, 1, 2, 3, then, on the arrival of the next can, the Digital