Friday, March 15, 2019

KIM-2e Half Time Update

Here is the halftime status for my RetroChallenge 2019/03 project "KIM-2e" a KIM-1 simulator for the Apple //e . To review, I am using Mike Willegal's SUPERPROTO card as a foundation for my project. I am adapting it to use the MOS 6532 RIOT, rather than the MOS 6522 VIA. I don't have a GAL programmer, so I am using my own logic (basically from the KIM-1 schematic) to decode everything. The system will use the Apple //e's inhibit function to keep the Apple's RAM off the data bus at the location the KIM-1 would expect to find the 6532. I am also building a keypad and display that is functionally the same as the KIM-1's. Of course, this is all just an exercise in entertainment since the Apple //e already has an excellent keyboard and display, and an easy to use system monitor. But the end result should be an Apple II that can run binaries for the KIM-1, unaltered and in their full glory. So, I will finally get to use my Apple //e to play Farmer Brown on a 7 segment LED display as it was intended!

It took a while to get my LED modules assembled. I ran into a few problems with the new pinout. mostly, the transistor legs are so skinny that they fall right out of the sockets if a resistor leg is in there. The jumpers helped wedge them in the socket, but order of operations was important, and the jumpers had to go in last. Here is my display BusBoard assembled, with most of the soldering complete.
On the main peripheral card, the adapter board for the MOS 6532 is complete, and hopefully functional. Some of the ICs are installed and wired up. I still need to add some more glue logic ICs and the header to connect to the keypad. I do not think I will have time to deal with the ROM. Instead I will just load the KIM-1 ROM into the Apple II RAM at the correct address.
I still have a lot of wiring to do here! I had a new idea on how to do some of the address decoding for a little more granularity, so there are some jumpers that I am in the process of moving. It is getting messy! On retrospect, the ICs could have been laid out a little differently for shorter address lines.

And finally, here is the mock-up of how the interface will look with the keypad and display board in the bottom half of the enclosure. Next, I need to solder in the header for the connector to the peripheral card and the socket for the display board, and add the decoder and buffer ICs on the bottom proto-board.

I will likely post a schematic of everything at the end of the month, but it is still undergoing so many changes as I go that I don't want to post anything yet. In the meantime, you can follow my status on this project at my RetroChallenge_2019/03 blog pages.

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