On 09/07/2013 04:43 AM, Bil Herd wrote: > 30 year old schematics for early TED. Will probably have better contrast on > the greyscales tomorrow. > http://c128.com/ted-drawings-1980s Neat... I also noticed the circuit for the disabling the internal RAM by pulling the _G pin of the TMS4416 high. This of course would still make write cycles reach the RAM since _G only disables the output. It would have been useful for external memory expansions, but not for anything that only temporarily disables the internal RAM. That would have needed a circuit to gate _CAS. As for your note about R/_W and driving it. VIC in the C64 doesn't drive it so once the 6510 is taken off the bus with AEC low, there is only a pullup on R/_w which doesn't give a sharp edge but a rather slow climb, kind of ugly, but works. The TED datasheet I have states that TED will drive R/_W HIGH in his part of the cycle, so I assume that there was another chip revision to add this little detail to TED? I assume that the chip engineers didn't think about it due to VIC. Gerrit Message was sent through the cbm-hackers mailing listReceived on 2013-09-07 17:00:13
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