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Specifications
Direct Hardware Control
In systems where the users program has direct access to the hardware (DOS)
the table below gives the mapping and functions that the PIO-32.PCI provide.
The address of each eight-bit port is calculated as shown in the table on the
following page, the cards base address plus an offset.
Reading the Inputs:
The inputs are active high. If an input is driven high (2V to 5.25 V) it will read
as a logical one (1), if driven low (0V to 0.8V) it will read as a logical zero (0).
If an input is not driven it will read as a one (1) due to the 10K ohm pull up
resistors on each port.
Reading the Outputs:
The value that is currently being used to drive the outputs will be returned.
Presetting an Output Port:
Each port has an output register associated with it. This register may be written
and retains its value whether the port is configured as an input or an output. To
preset the value of an output port the program should write to the port when it
is configured as an input then configure it as an output.
Writing the Outputs:
The outputs are active high. Writing a one (1) corresponds to 5V while writing
a zero (0) corresponds to 0V, at the output.
Port Configuration:
Each port can be configured as an input or an output by writing to its direction
control bit, refer to the table below.
Interrupts
Interrupts can be set up as shown on the following page. Port A1 bit zero is
the interrupt source(pin 47).
Sealevel Systems PIO-32.PCI
Page 12
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