Re: Paul was right

At 05:15 PM 7/24/97 -0800, you wrote:
>
>>Actually the 8051 is a nice instruction set. What about all that other
>>glue? Why not do all your outputs in software? I'm sure you can run the
>>2051 fast enough to keep up with any player, not enough outputs?
>
>Hmmmm. Actually I hadn't thought about it a lot yet. In retrospect, I
>suppose there's enough I/O that I could use a bit or two for "mode select".
>I was thinking of just having everything work simultaneously, but I guess
>that isn't necessary. Close a jumper and it's a G-80 spinner, open and
>it's a Midway spinner... That'd be kinda cool.

Actually I was thinking the same thing!

Read inputs
   Output G-80 spinner...
   Output Midway spinner...
   Output Dir & Clock...
   etc.
   loop

I was asking if you had enough *outputs* to do this. Of course you could
always:

Read inputs
   Output to external latch G-80 spinner...
   Output to external latch Midway spinner...
   Output to external latch Dir & Clock...
   etc.
   loop

>The 2051 is neat-- glue wise there isn't much needed. You need a clock
>source, just a cheap Oscillator or Crystal is OK, you could probably even
>get away with a little RC setup since speed variation isn't a big deal as
>long as it's fast enough all the time. Since the Flash (program) is
>onboard there's no need for an external latch to demux address and data
>like a "real" 8051. One thing I don't recall is how it deals with the data
>and program spaces-- maybe they're OR'd together on the Flash. Guess I
>should look that up before I get too excited about tables... ;-)

Even if you can't treat the flash as data, there is an instruction which
allows you to do a lookup in code space, your tables will work just fine.

The 17Cxx series of PIC processors also have an instruction for accessing
code space as a table, too bad they're expensive and don't come in any "one
chip does all" flavors. (Well at least they didn't four years ago...)

-Zonn
Received on Thu Jul 24 17:45:39 1997