Re: Tron progress halted (damn)

EvilJim wrote:
> I will check the version when I see the game later today.
>
> As for what I was seeing yesterday when working on the boards, not
> sure if can explain what was going on but I'll give it a shot. Going
> off of Brad's advice, I was investigating the LS138 decoder at E6 and
> its interaction with the memory chips.
> Using a probe I found that both the enables on D6 (2764, pins 20 &
> 22) were high, thus explaining why the memory was not enabled.
> Tracing this back to the LS138 gave me results of good Vcc and GND, as
> well as clock activity on both enables E1 & E3 (E2 tied to GND) and
> the addressing inputs (A0, A1, A2) to the decoder. On the output
> sides of things, there seemed to be an issue, as some of the lines
> seemed to be stuck high, including Select 4 (D6). Again, this seemed
> like a clear reason why D6 was not being accessed. At first I thought
> this was a good indication that the LS138 had indeed managed to give
> up the ghost.
> However, wanting to confirm exactly which addresses were or weren't
> being selected, and having access to one, I hooked up a logic analyzer
> in a further attempt to determine exactly what was going into the
> LS138 on the input side. If for some reason there was never a command
> to address D6, then of course it would never be enabled. When trying
> to acquire the bus activity the next time around, I found that I had
> stopped getting activity off the bus into the inputs of the LS138. So
> now I had nothing to trace...with no activity in, there was of course
> no activity out. Power cycle, nor board resets seemed to correct this
> situation. On a reset, there would be a brief (2-3 sec) period of
> activity, then all would go flat again.

The "brief (2-3 sec) period of activity" could just be the program
initializing and then halting until an interrupt happens. Check the
interrupt pins on the processor.
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Received on Wed Oct 31 16:33:30 2007