On Sun, 12 Feb 2012, William Levak wrote: > On Sun, 5 Feb 2012, Mike Naberezny wrote: > >> There you'll find a D80 image with a version of the editor that was >> improved by ISPUG (International SuperPET Users Group) members. One of the >> improvements is that the check for the dongle has been removed. I've >> verified that the editor does start up on a SuperPET with the 6702 removed. > > If the 6702 is nothing more than a dongle, then it is most likely a logic > array. Checking my old data books, I find the Monolithic Memories PAL 20 > series. These have enable on 1, ground on 10, clock on 11, VCC on 20, inputs > on 2-9, and outputs on 12-19. If you switch the inputs with the outputs, you > have a 6702. I quote from the 1983 data sheet for the Monolithic Memories: Another feature of the high end members of the PAL family is registered data outputs with register feedback. Each product term is stored into a D-type output flip-flop on the rising edge of the system clock. The Q output of the flip-flop can then be gated to the output pin by enabling the active low three-state buffer. In addition to being available for transmission, the Q uotput is fed back into the PAL to "remember" the previous state, and it alter its function based upon that state. This allows the designer to configure the PAL as a state sequencer which can be programmed toexecute such elementary functions as count up, count down, skip, shift, and branch. Since the SuperPet address lines are connected to the input pins of the 6702, an exact sequence of address on the bus prior to the read instruction may be necessary to produce the correct output. Also, the output data bits are individually programmable, so there may be a separate sequence to turn on or off each bit or combination of bits. wlevak@sdf.lonestar.org SDF Public Access UNIX System - http://sdf.lonestar.org Message was sent through the cbm-hackers mailing listReceived on 2012-04-23 06:00:04
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