PCI-DIO-120 Acces Digital Input/Output Card

The Acces PCI-DIO-72/96/120 Digital Input/Output Cards are parallel digital input/output cards designed for use in PCI-Bus computers. The same printed circuit board is used for all three models and is populated for 120 bits, 96 bits and 72 bits respectively. The card is 12.2 inches (310 mm) long and may be installed in any 5-volt PCI slot in IBM and compatible computers.

The cards are designed for industrial applications and should be installed in a long PCI slot of an IBM or compatible computer. Each I/O line is buffered and capable of sourcing 15 mA or sinking 24 mA (64 mA on request). The card contains Programmable Peripheral Interface chips type 8255-5 (PPI) to provide computer interface to the digital I/O lines. Each PPI supports three 8-bit groups A, B, and C. Each 8-bit group can be configured to function as either inputs or latched outputs. Group C can also be configured as four inputs and four output latches. The I/O line buffers are configured automatically by hardware logic for input or output use according to the PPI control register direction software assignment.

Outputs of the I/O buffers are pulled up through 10K resistors to +5VDC. Outputs can be changed to pull down by jumper selection on the card. This pull-up/pull-down arrangement assures that there are no erroneous outputs at power-up until the card is initialized by system software. The I/O buffers may be tristated under program control.

Two I/O Lines of each port can be used to interface User Interrupts to the computer. Interrupts of all ports (one per port) are OR'ed together and the Interrupt level is assigned by the system. I/O wiring connections are via 50-pin headers on the board. Every second conductor of the flat cables is grounded to minimize the effect of crosstalk between signals.