Keithley KPCI-PIO24, User Manual, Page: 16 / 66

KPCI-PIO24 User’s Manual General Description 2-3
Most existing application software and data acquisition packages work with the KPCI-PIO24
board. If you wish to reuse existing port I/O programs previously designed for ISA boards, refer
to information about the Hardware I/O Emulation driver included on your DriverLINX CD-
ROM. The Hardware I/O Emulation driver may be used only with Windows 95/98. Refer also to
“Setting control and data registers” in Section 4 of this manual.
Other I/O characteristics
Additional I/O port characteristics are summarized below:
• The KPCI-PIO24 can output higher currents than the industry standard 8255 chip. Output
current capabilities of 15mA (source) and 64mA (sink) allow it to control many LEDs, Opto
22 modules, and relays directly.
• The PA, PB, and PC ports can always be read/write accessed, regardless of the direction they
were initially configured for, without the external signal level being affected. For example,
when a port is configured as an output, it is still possible to execute a read of that port. The
data returned by the read is the data latched in the I/O register.
•
On power-up or whenever the computer’s hardware reset line is asserted, all ports are cleared
and set as inputs.
• The PA, PB and PC ports interface to user I/O connections via a standard 37-pin connector.
• Two externally accessible inputs allow for flexible interrupt configuration: INT_EN (exter-
nal interrupt enable, active low) and INT_REQ (external interrupt request, edge triggered).
• Computer power supply voltages are made available at the I/O connector for use in
external circuits.