Pinout for SED9421

[Philip Pemberton]

In message <4387794F.1020008 at jetnet.ab.ca>
          woodelf <bfranchuk at jetnet.ab.ca> wrote:

> Allison wrote:
> 
> >Either that a Dflop(74LS74), hex D-latch(74LS174) and 32x4 prom(74LS288).
>
> Just for the heck of it,  got a schematic and a prom listing?
> Did anybody ever use a serial chip and a data separater
> rather than a floppy disk controler?

Actually, I wouldn't mind taking a look at the appnote with the data
separator in it. Sounds like something that might be worth reading...

I've just spent two days reverse-engineering the Atari Digital Vector
Generator down to state machine level. Thank %DEITY for schematics!

Only thing I am trying to work out is why the hell the state machine jumps to
state 9 on startup, which is a DMALD microinstruction. Basically, when it
starts up, it pulls an address off the stack and jumps to it. Unless I'm
wrong, that means it jumps to a random address on startup. That is, unless
the LS670 Register File Memory used for the stack is guaranteed to power up
with all registers loaded with 0000(bin), but IMO that's a dangerous
assumption to make without testing.

Just a shame LS670s are pretty much unobtainium these days, otherwise I would
have tested it out...

Thanks.
-- 
Phil.                              | Acorn RiscPC600 SA220 64MB+6GB 100baseT
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