SC509, v1.0, User Guide

SC509 is a Z80 PIO card designed for Z50Bus.

The Z80 PIO card (SC509) provides two 8-bit parallel ports with handshaking and flexible input and output connectivity, as well as support for Z80 mode 2 interrupt daisy chaining.

Input signals are taken from both the top and the side headers.

Output signals are available on both the top and the side headers.

Input and output signals are nominally 0 volts (low/off) or 5 volts (high/on).

This card should be compatible with all Z50Bus systems.

Cards using Z80 mode 2 interrupts need to be grouped together on the backplane. These cards are linked by a daisy-chain which is incorporated into the backplane. As a result you must not leave an empty slot between any cards generating interrupts.

Details about programming a Z80 PIO can be found in the Z80 PIO datasheet (PDF).


The card responds to input/output addresses matching the address set with jumpers. When a jumper shunt is fitted, that bit must be a 1 (high voltage). When the shunt is not fitted, that bit must be a 0 (low voltage).

The card occupies 4 addresses, thus address bits 0 and 1 are not included in the address decoding. The board includes place holders for bits 0 and 1 for consistency with other cards in the SC500 series. It is suggested that you remove or cut the pins for bits 0 and 1 as a reminder that they are not used.

The recommended address for this card is currently 98 hex (10011000 binary) when used as part of an SC500 system. This address is selected by fitting jumper shunts for bit 7, 4, and 3.

Several of these card can be used at the same time providing the addresses are all different.

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