Digital I/O card for my Z50Bus computer
While working towards getting my LiNC80 SBC1 kits ready for sale, I had a little bit of waiting-time to cover. During that time, Steve Cousins and I were talking about his boot-up status output using a standard I/O port, and that it would be nice if I would be able to provide a digital I/O card a short time after launching the kits.
As I already had my prototype prototyping cards and a bit of time, I designed a card inspired by Spencer's RC2014 Digital I/O card, and assembled it using simple point-to-point wiring. As expected, the card performs exactly what it was designed to do, both when connected directly to the SBC and when connected to a 5-slot Z50Bus backplane.
This is a simple I/O card that uses a 74LS273 latch to receive and store output data displayed on eight LEDs, a 74LS245 bus tranceiver to "gate" the input switches/buttons as inputs, and a 74LS688 8-bit comparator to do full address decoding of 8 bits. The way the 8-bit comparator is used makes it possible for this card to use any single I/O address in the Z80 I/O address range. Writing to the selected address sets the output state, and reading the address reads the current values on the buttons/switches. Steve's SCMon uses the "reserved" address 0x30 as a simple output write port for status during boot, so setting this card's address to 0x30 allows the nice led-scroll to be seen 🙂
Based on the schematic below, I will start doing a PCB layout, and make this an official LiNC product as soon as the LiNC80 SBC1 launches proper.
Z50IOCard schematic - click for full resolution PDF
LiNC80 SBC1 kits are available for purchase!
I am proud to announce that as of now, my LiNC80 SBC1 is available for purchase in kit form at Tindie!
It took me a few tries to get through the approval process, simply because the fairly high differences in the fairly high shipping costs incurred from using Posten Norge as my trusted carrier, forced me to make separate listings of Kit and PCB, and that caused issues, as Tindie weren't used to dealing with that.
I'm not sure if this is the culmination of or the start of a lot of hard work. Now starts the bit where I need to ship, restock, support and see what people make of it. But first of course the terrifying bit: will anyone actually purchase the kit?
If you want a compact, expandable, fun 8-bit retro computer reminiscent of 1979, head on over to my Tindie shop now!
