I'd do that with a microcontroller, an EPROM and like :) Nice project
:D
No microcontroller required - it's already just a handful of TTL chips.
Why use a handful of ttl chips if I can do the same with a pair? :o)
Firstly I object to this idea that every digital project has to include a
microcontrolelr (in fact that's why I stopped reading Circuit Cellar
magazine!'. Yes, microcontrollers are very usedul, and I use them myself
when I consider them to be appropraite. But not for everything
Now lets look at this device. From what I understand it has to step
through the contents of an external EPROM under the control of some
signals from the VT78. The outputs of the EPROM are fed back to the VT78
(possily after going through a buffer). So the microcontroller would
replace the address counter and handshake logic.
You need a microcontroller with a fair number of I/O pins for that,
proaly a 8751 or something. If you don't have a programmer for that, you
need to hanf an EPROM off it containing the firmware (which then means an
address latch) But even if you do, it's a 40 pin chip to wire up. Five
TTL chips are peoably only twice as many pins to wire, if that..
Then there's the thign that I can wire pins (and design TTL circuits) a
lot faster than I can write microcontroller firmware. Period. Of course
once I've written the firmware, I can program aas many microocontrollers
as a I want, but this is hardly going to e a large-volume project.
I think I could wire up the necessary TTL chips in less time that it
would take me to type-in read-written source code, assembly it and
program it into a microcontroller.
-tony