inputs and four output latches. Pull-ups on the card assure that there are no erroneous outputs at power up
until the card is initialized by system software.
Tristate I/O line buffers (74LS245) are configured automatically by hardware logic for input or output use
according to direction assignment from a control register in the PPI. Further, if a jumper is properly placed
on the card, the tristate buffers may be enabled/disabled under program control. (See the Option Selection
section to follow.)
I/O wiring connections are via 50-pin headers on the board. Two flat I/O cables connect the card to
termination panels. Also, this provides compatibility with OPTO-22, Gordos, Potter & Brumfield, et al
module mounting racks. Every second conductor of the flat cables is grounded to minimize crosstalk
between signals in the cables. If needed for external circuits, +5 VDC power is available on each I/O
connector pin 49. If you use this power, we recommend that you include a 1A fast-blow fuse in your circuits
in order to avoid possible damage to the host computer or cable in the event of a malfunction in those
external circuits.
The card occupies sixteen bytes of I/O address space. The base address is selected by the system. An
illustrated setup program is provided on diskette with the card. Interactive displays show locations and
proper settings jumpers to set up the interrupt enable function. Also, sample programs in Turbo-C and
Turbo-Pascal are presented in the Software section of this manual.
Manual PCI-DIO-48(S)
6
