The parallel I/O interface card

This digital I/O card is a product of MicReD Ltd., proprietary Windows device drivers are shipped as part of the software installation kit.

Figure 6-2: The parallel I/O interface card

This card interfaces digital I/O signals (up to 48 bit) to the I/O bus of an IBM compatible PC, by using two 8255 PIO ICs. In order to enhance the noise immunity and the driving ability all the I/O lines are buffered. The direction of the bi-directional buffers can be set with panel jumpers, according to the software configuration of the 8255 PIO-s.

Technical parameters:

• 2x8255 parallel interface IC
• 48 digital I/O channels, TTL levels
• Organized in 4x8-bit and 4x4-bit groups
• All I/O channels are buffered
• Interrupt handling
• Can be plugged into a standard ISA connector socket on the IBM PC motherboard
• Rear connector: 37 pin D type, male
• (1^st 8255 IC: LA, LB, LC_H, LC_L ports)
• Panel connector: 38 pin, male
• (2^nd 8255 IC: HA, HB, HC_H, HC_L ports)
• Base address: set by DIP-switch
• IRQ line number set by panel jumper

Standard accessory of the card: cable from the panel connector to a 37 pin D type, female rear connector.

I/0 parameters of the card are set by the DIP-switch in the middle. Factory default settings are good for most of the cases.