Hello, * On Sun, Sep 16, 2012 at 11:07:54PM +0200 silverdr@wfmh.org.pl wrote: > On 2012-09-16, at 21:48, Spiro Trikaliotis wrote: > > Also, have a look at the VIC20 schematics, it has the same circuitry. > > But it doesn't have all the features of a 64/6510, does it? I mean > AEC, the $00/$01 port, tape is connected to VIA.. I did not know this before, but: The VIC20 also uses the circuitry for AEC, it's done explicitly. But you are right, I completely forgot about the on-chip IO port of the 6510. That's not present in the VIC20. > You mean which circuitry is the same? What can I learn from it that > could be used in a 64 to implement the missing elements? The VIC20 uses AEC, but with discrete chips, not on-chip like in the 6510. Have a look at http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/vic20/251027l1.gif (VIC20 CR): To the left, there is the 6502. Directly nearby it, there are UF8, UE8 and UD8 (all 74LS245) which are used to tristated the address bus (UE8 and UD8) as well as the data bus (UF8). At http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/vic20/324001_1.gif, you can also see better where the -E lines of the LS245 come from: For the address bus, it is directly from the 6560/61, for the data bus, it is active (=0) when the decoder does not select any memory area, and a (modified) PHI2 is is high. Connecting all -E together to form an -AEC seems to me to be exactly what the 6510 does. For the 6510, only the on-chip port would have to be added (and, when addresses 0 or 1 are selected, -AEC should be forced to high.) Regards, Spiro. -- Spiro R. Trikaliotis http://www.trikaliotis.net/ Message was sent through the cbm-hackers mailing listReceived on 2012-09-17 18:00:43
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