heuser.marcus@freenet.de wrote:
Its a parallel I/O and not a drive controller. These boards can be used
to control peripheral devices like printers, home appliances, custom
switchboards, railroad models, roboters etc.
The 6522 is a "VIA" chip ("Versatile Interface Adapter"), the D1 and D2
probably refer to the two 8 bit parallel ports of the chip.
It has more features and because it's "versatile" it was often used and
datasheets and programming info is readily available for it (if you are
inclined in using it).
Does the card have a ROM or EPROM on it? A chip with 24 or 28 pins -
there usually is a number on it with 4 or 5 digits, starting with a
"27".
I've always had a fondness for 6522-based cards (like the Mockingboard) since they have two counter/timers and two bi-directional parallel ports (plus handshake lines), and can generate interrupts. It's a very versatile card, and you can terminate the data cables (D1 and D2) in any way that is useful for your purposes. Most 6522-based cards did not contain EPROMs (unless they were intended to interface with printers), but software is usually written for each specific purpose to which they are applied. A little tracing of address wires will usually confirm that the chip's 16 registers are mapped directly into the /DEVSEL space ($C0sx). -michael Music synthesis for 8-bit Apple II's! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it is seriously underused."