SV: Re: [sdiy] SV: 8254, was:Roland DCOs

[karl dalen]

Because there was not much else to chose from back in those days! :-)
Anyhow a short list of DCO 8253/54 as you proposed, just for fun:

SX210
Sx240
Bit01
Bit99
AX80
Juno6
Juno60
Juno106
Juno Piano
JX8P
JX3P
JX10
Mks70
Mks30
Poly61
Matrix1000
Matrix6
Matrix6R
Cheetah MS6

Reg
KD
--- Bob Weigel <sounddoctorin at imt.net> skrev:

> 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
> >
> >
> >
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