jnc at mercury.lcs.mit.edu
Tue Jul 21 08:25:58 CDT 2015
> From: Guy Sotomayor
> I took some time off from working on the MEM11 ... I had some time over
> the past few days, so I spent it working on the simulator.
> Right now all of the J1 instructions seem to simulate properly.
I had to go hunt up your original message:
to refresh my memory as to exactly what a 'J1' was!
It was interesting to re-read your original message; I and a couple of other
people are looking into doing a QBUS card to provide access to modern
non-volatile storage (SD cards, USB thumb drives), and in discussing the
internal design, we'd planned on an FPGA, and a separate micro-controller.
Your concept to have the 'micro-controller' _in_ the FPGA is interesting! The
only problem, from our point of view, is the 'limited' number of FPGA pins
(the QBUS interface alone is ~50 pins) - at least, without going to a BGA
part, which we view as undesirable.
> Everything related to the basic simulator also seems to be functional.
I'm curious as to your reasoning in doing a custom simulator (OK, it's all
fun :-). I do understand having _a_ simulator (writing all the software
involved on the card will be much easier if you don't have to deal with a
flaky/new hardware), but since the J1 is in the FPGA, couldn't you just use
the FPGA simulator? Or is it too slow to emulate a good-sized J1 program?
PS: When we get down to detailed design, we'll have to get the specs on your
light panel interface; we'd like to be able to drive the same light panel
(for exactly the same uses :-), to avoid re-building the wheel.
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