Manual PCI-IDIO-16
5
Chapter 1: Introduction
The card is a half-size card that provides isolated digital input and output interface for PCI-Bus
computers. The card has 16 optically-isolated digital inputs for AC or DC control signals and 16 solid state
switch outputs. An interrupt can be generated when any of the inputs change state to free up computer
resources by eliminating the need for constantly polling the card. This card occupies eight consecutive 8-
bit registers in I/O space.
Inputs
The isolated inputs can be driven by either AC or DC signals and are not polarity sensitive. Input signals
are rectified by a diode bridge and applied to a transistor circuit that provides constant current drive to the
opto-isolator independent of the amplitude on the input. Input voltages of 2.5-50VDC or AC voltages of
2V- 36Vrms can be accepted. Inputs have a 0.2V hysteresis. Each input circuit contains a switchable
slow/fast filter that has a 5 millisecond time constant. The filter must be selected for AC inputs in order to
eliminate response to zero crossings. The filters can also be useful with slow DC input signals in a noisy
environment. The filters are under software control. All filters may be turned on by a read at base address
+3. All filters may be disabled by a write to base a3. The filters for the first eight inputs can be
turned on and off individually by a write at base a7; a value of one in the bit corresponding to the
input will turn that input’s filter on, while a value of zero will turn it off. The status of the first eight input
filters can be read back at the same address.
Interrupts
When enabled by a software read to base a2, the card asserts an interrupt whenever any of the
inputs change state. Once an interrupt has been generated and serviced, it must be cleared. A software
write to base a1 will clear an interrupt. This interrupt capability may be disabled by a software
write to base a2.
Outputs
The digital outputs are comprised of fully protected high-side FET switches. The FETs have built in
current limiting and are protected against short-circuit, over-temperature, ESD and inductive load
transients. The current limitation is activated until the thermal protection acts. The switches are in the off-
state upon power-on or reset. Data to the output is latched by a Write to the base address and to base
4. The On/Off status of the switches can be read back by a Read command from the base
address and base 4.
