Each I/O line of this card is buffered and capable of sourcing 32mA, or sinking 64mA. The board simulates Programmable Peripheral Interface chips (PPI) to provide a computer interface to digital I/O lines. Each PPI supports two 8-bit ports (A, B) and two 4-bit ports (Chi, Clow). Each port can be configured to function as either input or output latches. The I/O line buffers (types 74ABT240 and 74ABT245) are configured automatically by hardware logic for input or output according to the PPI Control Register direction software assignment. Outputs of the I/O buffers are pulled up through 10KO resistors to +5VDC. I/O wiring connections are via 50-pin headers on the board. This provides compatibility with OPTO-22, Gordos, Potter & Brumfield, Western Reserve Controls, etc. module mounting racks. Every second conductor of the flat cables is grounded to minimize crosstalk between signals. If needed for external circuits, +5VDC power is available on each I/O connector at 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. The card occupies 32 addresses within the PCI I/O space. The base address is assigned by the system. Refer to the Option Selection Section of this manual for a detailed description.