These are economical 24- and 96-bit half- and 3/4- size cards respectively. A Programmable Peripheral Interface chip, type 8255-5, provides three 8-bit ports (A, B, and C) for each 24-bit group. Each port can be independently programmed for either input or output. Port C can also be configured as two 4-bit ports. These cards fully implement Mode 0 of the PPI chip. (Consult factory if you desire to operate in Mode 1.)
Model IOD-96M is electrically and software interchangeable with the Keithley Metrabyte model PIO-96 and the Computer Boards Inc Model CIO-PIO96. IOD-96E and IOD-96M have added capability compared to the two competitor units in that external interrupts can be supported under program control. Two lines on Port C can be used for this purpose. Bit C7 can accept inputs to enable/disable this interrupt capability and Bit C3 can accept the external interrupts. If the cards are to be operated in this mode, jumper placement on the card permits selection any one of levels #2 through #7. Interrupts from all four ports (one per port) are OR'ed together.
Card I/O bus address selection is by DIP switches on the cards. The 96-bit cards use 16 address locations on the computer I/O bus. Input/Output connections to IOD-24E are via a 50-pin connector. I/O connections to the 96-bit cards are via four 50-wire ribbon interface cables that extend through rectangular cut- outs in the mounting bracket and plug into headers on the card. IOD-96E and IOD-96M units required to meet EU "CE" requirements are supplied with blank mounting brackets. That permits you to use cabling methods that best fit your application. Strain relief is provided for these cables. Ready-made displacement type ribbon cables are available from ACCES as p/n CAB50F-xx. Alternate wires are connected to ground to provide shielding and minimize crosstalk.
On power-up or reset, all ports are automatically configured as inputs. This prevents spurious outputs. Before use, of course, each PPI should be software configured by writing to it's control register.
