Inspiration for this mode I found on Daryl's Computer Hobby Page. Daryl made Composite Video Text/Graphics Display based on ATMEGA8 and drive by VIA6522. This article will show how to build, assembly and connect VIA 6522 IC to Atari and use 2 additional 8-bit parallel ports and serial interface. This is my own project build from scratch but it's nothing modern - this IC was used in C64 to communicate with disk drive. It will be used as additional PIA for manage other equipment.
Why?
Well, on the market you may find a few sellers which have VIA6522, but...
- this IC is discontinued, don't wait so much time, buy it!
- it's still very useful and may be good alternative for PIA 6520(6521).
- topology and registers covering PIA 6520, so you may use it as equivalent for it. (some pins should be swapped)
- very cheap IC (~2$/piece).
Prototyping and Manufacturing
As last time (SRAM 512k extension module) I made the schematic and PCB using KiCAD (actually I'm so surprised how good is this software!). Below you may find schematic and PCB layout:
- Prototype on the BB
- Prototype on the BB
- Prototype on the BB
- Prototype on the BB
- PCB without polygons
- PCB with polygons
PCB without elements:
- 3D view
- Arrived PCB
Actually it's very easy and dummy test - just only for checking that 6522 working properly:
Enter the short program in BASIC interpreter and type RUN:
Code: Select all
10 ? PEEK(54528);: ? " ";: ? PEEK(54529)
20 GOTO 10
RUN
What next?
Well many ideas to do. Now you have independent ports. For example you may steering 64 LED matrix... using SERIAL port and many many more... I'll try to build additional display adapter as mentioned on the beginning of the article.