On 09/05/2012 08:24 PM, Rhialto wrote: > On Wed 05 Sep 2012 at 06:38:29 +0000, William Levak wrote: >> >> The original SuperPET contains sockets for four 6702 daughter boards. > > Perhaps that is why the output value is visible on 4 address locations. > The addresses influenced by the circuitry around the 6702 are more than > just those; all of "E F xxx0 xxxx" are affected, but the ones that are > not EF00 .. EF03 all return FF (instead of the EF of the unconnected > space). Apparently part of the address decoding is done inside the 6702. Another question... Was there only one 6702? Or was it like the 6530 where you had another number on the chip to indicate what's in there? I tried to find a photograph of the 6702, but wasn't able to. Also, the schematic http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/SuperPET/324055.gif shows a 74LS138 for decoding part of the address space and also a lot of CS signals on the 6702 itself. This schematic decodes the chip to EF8 00xx though, assuming the logic of the CS-signals is as shown. Gerrit Message was sent through the cbm-hackers mailing listReceived on 2012-09-05 19:00:45
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