Barring
implementation of 65SPI on a CPLD, is there a quick-n-dirty way
to wire up a SPI-based module to an Apple II/II+/IIe? I'm looking for a
temp solution, while I design a Apple II board with a correct
interface. Something that doesn't require any soldering would be grand
(bit banging the SPI via some IO pins, Using the DSR/DTR/RTS pins on the
RS232 (if that can be done...), etc.
SPI bus is a great way to add IO peripherals and mass storage to a system.
It's a simple synchronous serial bus and timing is fairly easy. I use it to
add a solid state disk to my systems using a SD or MMC which is a SPI
interface (SD has a wide mode too, but I don't use it).
Bit banging is the way to go. You only need two output bits and one input.
The outputs are clock, data-out and the input is data-in. CS/ on the part
can be held low if there is only 1. Data rates around 20-50KBits/Second
are not too hard to do.
The serial port if if has full modem controls, has enough bits but you will
have to develop correct voltage levels as they will be +-12V RS232
signaling.
A parallel printer port ids ideal as most have at least output bits and
2 input
(ready and paper out) and they are TTL.
If course a few simple TTL chips on a board can create a port for any
AppleII
or similar. IT would be a simplified version of a parallel printer port.
Allison
