chergr@lure.latrobe.edu.au (06/04/91)
Interfacing a Mac to the outside world can be done in a number of ways:
1. Join the Mac to a small microcomputer with a serial line.
Pros:
easy to electrically isolate your expensive Mac from the hardware
good for controlling things on the 10microsecond timescale.
Cons:
need to program the Mac and the microcomputer
data transfer rate is limited by the Mac serial chip.
Commercially available units exist, or build one yourself
based on a Forth based micro.
2. Join the Mac to dumb hardware which generates serial data
and reformat the data by direct software access to the serial
chip in the Mac. MacRecorder does this.
Pros and Cons same as above but less flexible.
3. Use the SCSI port as a parallel port.
Pros
Data transfer rate is fast.
Cons
You cannot use a SCSI hard disk unless your hardware
is smart enough to understand the SCSI protocol.
4. Use a Mac Plus, build a small daughter board to plug into
the ROM socket, take a cable from the daughter board to the outside
world. A Doctor Dobbs article described this approach for attaching
a SCSI chip to a Mac 512.
Pros
Data transfer rate is fast
Cons
Need to understand the Mac address map
5. Use an original Mac SE, build a small card to fit inside
the Mac with address decodeing and buffering. Take a subset of the
address data bus outside the Mac on a cable.
Pros
Same as 4 above
Cons
Same a 4 above
Also mention that the Mac can be damaged by electrical
failures in the hardware.
The software may have to understand about interrupt handling
in the Mac environment.
Commercial borads exist already.
6. Buy a Mac II and buy a commercial NuBus card
Pros
Colour is nice for data.
Cons
3kV in a Mac II is highly depressing
I have used a number of these approaches but mainly the first one.
Hope this makes sense
Regards Dr Richard Rothwell ( the overpaid electronics tech )