User guide

P/N: 021-00154, Rev. A.6 - updated for V4.7 Tools Page | 29
A typical digital input waveform as seen at the DVC digital input pin looks like the following:
+PWR
De-bounce Time Time
The DVC5/7/10 support two electrical configurations called Sinking and Sourcing. In the Sinking case, the
switch is powered externally and the digital input pin detects the switch being open or closed and supplies a
connection to ground through a resistor for the current when the switch is closed. In the Sourcing case, the
DVC supplies the power (i.e. +5vdc reference voltage through a 1k ohm resistor via a second DVC reference
pin connected to the digital input) for the switch as well as the digital input pin where the switch being open or
closed is received. The DVC5 and DVC10 have 4 and 6 reference pins respectively. The DVC7 has a single
+5vdc regulated Reference output capable of driving up to 500ma of current. If you use a reference output for
a switch on the DVC5/10 controllers and you wish to check the Reference pins voltage (to detect miswiring or
other abnormal conditions) you can do this using the Analog input or Universal input configuration name for the
particular reference pin you intend to use. To use a Digital Input in sourcing mode on a DVC7, an external
series resistor must be used to limit the current sourced from the internal reference voltage regulator to
prevent shorting the reference voltage to ground through the inputs switch. A 1K ohm 1 Watt resistor will
protect the reference voltage regulator from shorts to ground and shorts to power in.
The two configurations of digital inputs supported by the DVC hardware are:
Sinking (Externally Powered Switch) Sourcing (DVC Ref Voltage Supplied)
Note: the DVC circuitry senses the voltage change at the edge of the
waveform and if the transition state is the same after the de-bounce time
interval then the new state is deemed valid and communicated to your
application via the input’s variable name True or False setting.
To configure a digital input, click one of the Digital Input buttons on the DVC
screen. The Name field’s value is the way this input will be referenced in your
user application.
The De-bounce Time
setting is used to avoid recording momentary spikes
on the input as valid state changes. The polarity
determines what voltage
level is interpreted as a true or false or which edge causes a change in the
state of the input. An explanation of how the DVC interprets inputs. In No Toggle, the state of the input flag
will change to True any time the Active Polarity Input condition is met including debounce time and back to
+ PWR
( +3Vdc to +32Vdc)
to DVC DIGITAL IN
Pin (10k ohm resistor
to PWR COM)
PWR COM
to DVC DIGITAL IN Pin
(10k ohm resistor to PWR COM)
to DVC POT REF Pin
(1K-ohm resistor connected to +5v
or DVC7 500ma regulated
reference)