Pinout for SED9421

[woodelf]

Philip Pemberton wrote:

>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...
>
>  
>
umm  33 cents each at  unicorn electronics.   Could the  stack  be 
jamed  with  0  on reset?
Ben alias woodelf
 

>Thanks.
>  
>