On 2012-11-23, at 18:43, silverdr@wfmh.org.pl wrote: >>> I just had a look at the schematics of the narrow board and I wonder what the A14 is doing at the U4 (23128).. >> >> Remember that BASIC ROM and KERNAL ROM in the C64 are not 'next' to each other. There is a 8 KB gap between them. So in order to select the correct 8 KB block in the 23128 ROM, you can't use A13. It would be HIGH at $A000-$BFFF and $E000-$FFFF. But you can use A14 since that is LOW at $A000-$BFFF and HIGH at $E000-$FFFF. > > That's clear but what I am wondering about is what do 15 address lines do at 16KiB ROM. And seem to be all connected. Or the guys just connected A14 from the bus to A13 of the ROM.. ? Have to check the 23128 pinout. OK - I was fooled by the inaccuracy on the drawing. There is only 14 lines as expected and the A14 from the bus is connected to the A13 of the ROM, which makes sense. -- SD! Message was sent through the cbm-hackers mailing listReceived on 2012-11-23 18:01:17
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