🚀 go-pugleaf

In article <QZlhy*Nkh@laosinh.s.bawue.de>, Gerrit Heitsch (gerrit@laosinh.s.bawue.de) wrote:
> In article <4iq3ev$hm5@serpens.rhein.de>, Michael van Elst writes:
(...)
> > 
> > Wie waers mit der seriellen Schnittstelle ?
> 
> Noe, das Schieberegister hatte der 6522 auch schon, rate mal, wie die
> alten CBM 4032/8302 ihre 'Toneffekte' produziert haben.
(...)
Schamloser Klau aus "CBM Hacking #9":

[ IEEE 488 seriell a la Commodore]
...
        And here is what Jim Butterfield followed up with:
        
        "Technically, the idea was sound:  the 6522 VIA chip has a "shift
        register" circuit that, if tickled with the right signals (data and 
        clock) will cheerfully collect 8 bits of data without any help from 
        the CPU.  At that time, it would signal that it had a byte to be 
        collected, and the processor would do so, using an automatic 
        handshake built into the 6522 to trigger the next incoming byte.  
        Things worked in a similar way outgoing from the computer, too.
        We early PET/CBM freaks knew, from playing music, that there was 
        something wrong with the 6522's shift register:  it interfered with 
        other functions.  The rule was:  turn off the music before you start 
        the tape!  (The shift register was a popular sound generator).  But 
        the Commodore engineers, who only made the chip, didn't know this.  
        Until they got into final checkout of the VIC-20.      
...
        When the 64 came out, the problem VIA 6522 chip had been
        replaced by the CIA 6526.  This did not have the shift register 
        problem which had caused trouble on the VIC-20, ....
 
Zitat Ende. Voller Text (~4000 Zeilen) auf Anfrage. Keine Flames bitte, ich
habe mir das nicht aus den Fingern gesogen, kann es aber auch nicht ueberpruefen.
          
- Harald