[sdiy] SV: 8254, was:Roland DCOs

[Bob Weigel]

In case nobody mentioned this...I've been pretty busy here...the 8253 is 
by far the most common chip I've seen in DCO circuits.  Kawai's 
SX-210/240 I think both use it, (at least the latter) and the Crumar Bit 
Series (01, 99, One), ..I think the Akai AX80 too I believe.

karl dalen wrote:

>--- Ingo Debus <debus at cityweb.de> skrev:
>  
>
>>We tried Intel, AMD and another manufacturer (forget which) whose '54  
>>were even spec'd for an input frequency of 12,5MHz. We also tried the  
>>non-CMOS version (8254 instead of 82C54). They all showed this  
>>behaviour. The 8253 worked flawlessly however, but is only spec'd for  
>>a much lower input frequency.
>>    
>>
>
>Peculiar! 
> > 
>  
>
>>>Also there are plenty of clones under different labeling,
>>>altought 8253, 8254 was the system timer chip in 8088 286, 386 PC's  
>>>for
>>>quite some time. Inside those old PC's there are loads of these chips
>>>in them particularly 8088-86.
>>>      
>>>
>>Yeah, that puzzled me a lot. How come that chip never caused problems  
>>in PCs?? I don't know for sure, but I suspect in a PC the chip was  
>>not often accessed from the processor side.
>>    
>>
>
>I guess it was simply written once, for example to generate a
>timed interrupt in square mode or narrow PW mode.I remember 
>the brand uPD as quite a reliable timer clone.
>
>  
>
>>In my design the '54 ran  
>>smoothly forever as long as the processor didn't read from or write  
>>to it. That also made me suspect that tWC and tWG timing was  
>>critical. Ah, memories come up again...
>>    
>>
>
>Usually in a DCO application the timer are set to toggle 50/50 and no
>edge/flank manipulation, maybe that was enough so the timer didn't fuck around?
>
>Reg
>KD
>
>
>
>      __________________________________________________________
>Går det långsamt? Skaffa dig en snabbare bredbandsuppkoppling. 
>Sök och jämför hos Yahoo! Shopping.
>http://shopping.yahoo.se/c-100015813-bredband.html?partnerId=96914325
>
>
>_______________________________________________
>Synth-diy mailing list
>Synth-diy at dropmix.xs4all.nl
>http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>
>
>  
>