Xylem System 5000 User Manual - Manual (Page 38)

Digital In
The Digital I/O Ports are located on the
lower first block of the front panel. The
first port of the block is the Digital ground
(Dgnd). As Inputs, the digital signal has
an internal pull up resistor of 47K Ohms.
This allows a switch closure to ground to
activate the input. It can also be driven
using normal logic levels.
INPUTS
36
Port(s)
Defines which port is currently being
measured and will be used as the Task
Value.
Mode
Defines the current mode of the Digital Input. Digital Inputs have four modes of operation: Level,
Frequency, Event Counter, and Quad Counter. Level and Event Counter Modes allow the Edge
Triggered (Event-driven)Type to be used.
Level
The default mode for a Digital Input is
Level. This Digital Value gives the current
state of the digital I/O pin. As an Input, the
value will be a 1 or a 0 meaning “On” or
“Off” respectively. If the pin value is a 1,
the input voltage will be approximately 3.5
volts or higher, (normally 5.0 volts). If the
pin value is a 0, the input voltage will be
approximately 0.8 volts or less, (normally
0.0 volts). The range between 0.8 and 3.5
is not defined and may be either a 1 or a 0.
This Mode could be used to test the status
of an external device, such as a motor. The
digital I/O pin would be used as the
source for data; a 1 would be measured if the motor was on, a 0 would be measured if the motor
was off.