On Wed, 5 Sep 2012, Gerrit Heitsch wrote: > 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. My 6702 says MOS MPS6702 4581 > 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 list > wlevak@sdf.lonestar.org SDF Public Access UNIX System - http://sdf.lonestar.org Message was sent through the cbm-hackers mailing listReceived on 2012-09-06 07:00:42
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