SkalTura Posted September 29, 2021 Share Posted September 29, 2021 Anyone any experience with the bankswitch cartridge from PixelPast (http://www.grandideastudio.com/pixels-past/)...? Made one using the F8 program in the PLD, and Ms.Pacman (8k) but all I get is a black screen. There is no mention in the description of the card, but I wonder if I should fill the 27C256 with the same game multiple times ? Now I just programmed the 27C256 with 1 time Ms.Pacman, and filled the blank space with "FF", just like I would do on any other Eproms. Anyone ? Quote Link to comment Share on other sites More sharing options...
alex_79 Posted September 29, 2021 Share Posted September 29, 2021 52 minutes ago, SkalTura said: Now I just programmed the 27C256 with 1 time Ms.Pacman, and filled the blank space with "FF", just like I would do on any other Eproms. If I'm understanding correctly the "F8" pld source code from the page you linked, pin 26 (not connected on a 2764, address A13 on a 27128 and 27256) is always low, while pin 27 (/PGM on a 2764 and 27128, A14 on a 27256) is always high. Which means that if you're using a 27256 for a F8 game, the rom must be burned starting from address 4000 (hex value). So you'll have 16k of unused space, then the 8k rom, then another 8k of unused space. 2 Quote Link to comment Share on other sites More sharing options...
SkalTura Posted September 30, 2021 Author Share Posted September 30, 2021 Ah, okay... I will try that. Thanks! Quote Link to comment Share on other sites More sharing options...
SkalTura Posted September 30, 2021 Author Share Posted September 30, 2021 Yes, that did the trick... Many thanks !! 1 Quote Link to comment Share on other sites More sharing options...
+SvOlli Posted September 30, 2021 Share Posted September 30, 2021 Just as a rule of thumb, I always mirror up the data on an (E)EPROM, when using a larger one than needed. It had never failed me so far, and even works if the most significant address bit(s) is/are floating. And I've seen guys trying to pull lines up/down using resistors to match the part of the EPROM they use. In theory it should work, practically they've fallen back to mirroring the data to get it stable. Pro-tip: look for some cheap 27SF256 EEPROMs. They can be used as a drop-in replacement for the 27C256, but can be reprogrammed without the UV-light step, similar to a flash chip. For these I've also got boards using zif-sockets for easy changing of the chip. One of 4k, F8, F6, and F4 each. Quote Link to comment Share on other sites More sharing options...
SkalTura Posted October 1, 2021 Author Share Posted October 1, 2021 (edited) 8 hours ago, SvOlli said: Pro-tip: look for some cheap 27SF256 EEPROMs. They can be used as a drop-in replacement for the 27C256, but can be reprogrammed without the UV-light step, similar to a flash chip. For these I've also got boards using zif-sockets for easy changing of the chip. One of 4k, F8, F6, and F4 each. I have a UV box, so I don't mind erasing the chips. Usually keep the failed or old Eproms in a separate box, and erase then all at ones when I have 10 or so... I'm actually working on a cartridge that supports multiple F8 games, but wanted to try the PLD cart first to figure out if that was useful to me. So eventually I will indeed use a EEprom, maybe 4M or 8M so store several 8k games. Work in progress... Edited October 1, 2021 by SkalTura Quote Link to comment Share on other sites More sharing options...
SkalTura Posted October 2, 2021 Author Share Posted October 2, 2021 Don't know if anyone ever thought of this, but just in case... Here are my findings... The PixelPast bankswitch card works as expected, using the F8 file for 8k games in the PLD, and a 27C256 Eprom. Since only A12 on the Eprom is used for bankswitching, A13 and A14 (as mentioned in the PLD file (thank you alex_79)) are only used to select where the game is started from. So I loaded 4 different 8k games in the Eprom and disconnected A13 and A14 from the PLD. Connecting A13 and A14 to either +5V or to ground, selects one of the 4 games. Games in the Eprom, in this order were: - Ms. Pacman - E.T. - Galaxian - StarGate Worked perfectly for Ms. Pacman and E.T. Galaxian started scrambled. SartGate didn't start at all. But to be honest, I tested this on a breadboard with about 50 wires connecting the PLD to the Eprom and the Atari connector, so a bit of instability was to be expected. I will make a PCB for it soon for more testing. And I guess it will also work for a F6 (16k) bankswitch card, selecting the games with only A14 (and A15 if you use a 27C512) Quote Link to comment Share on other sites More sharing options...
SkalTura Posted October 3, 2021 Author Share Posted October 3, 2021 (edited) Designed a PCB that can be used for 2k/4k games, but also 8k, 16k and 32k games. Using the jumpers, you can select what type of bankswitching you want to use (F8/F6/F4, or no bankswitching). And with the rest of the jumpers, you can select different games. It uses a 1024k Eeprom (29F010 in my case), and a 20V8 PLD just like the PixelPast cartridge. So if you want to use 16k games for example, put jumper F8 and F6 sideways. The A12 and A13 signals from the PLD will then go to the Eeprom. The other jumpers can then be put to either up/down (+5V or Ground) for selecting 8 different games. If you want to use it for normal 4k games, use all jumpers to either +5V or Ground for selecting 32 games. Bankswitching is then not used, so the output of the PLD is only used for the Chip Enable signal. NOTE: Only tested with an (unstable) breadboard setup, so I will need to make the PCB to see if this is indeed a stable working solution... NOTE: Not sure if the PCB fits in all cartridge cases, but it does fit in the one I have. It think it was the case from Asteroids, but its been so long ago that I'm not sure of this. Edited October 3, 2021 by SkalTura 3 Quote Link to comment Share on other sites More sharing options...
SkalTura Posted October 30, 2021 Author Share Posted October 30, 2021 The unstable breadboard setup with many many many wires was working fine. Sometimes wiggling the wires was needed, but E.T (8k) started without much trouble. Once the wires were stable, I've restarted the Atari about 20 times and it always started E.T. So I designed the PCB for it, as shown in the previous post and had the PCB made. Received the PCB's a few days ago, and soldered one together for testing (don't mind the "F6", that was from a different test). But for some unknown reason it doesn't work at all, and I can't seem to figure out why. I've even tried it with the F8 PLD and 27C256 Eprom that were on the breadboard setup, but nothing. So I stuck the PLD and Eprom back on the breadboard, and it started first time... Super annoying !! Back to the drawing board ? 1 Quote Link to comment Share on other sites More sharing options...
SkalTura Posted November 1, 2021 Author Share Posted November 1, 2021 Did some measuring, turns out that the PCB's are not correctly made. My design is correct, but for some reason the PCB manufacturer didn't make all traces going to the Eeprom ? 1 Quote Link to comment Share on other sites More sharing options...
SkalTura Posted November 8, 2021 Author Share Posted November 8, 2021 The PCB manufacturer sent me a new set of PCB's, and now it is working fine... :-) 2 Quote Link to comment Share on other sites More sharing options...
SkalTura Posted November 12, 2021 Author Share Posted November 12, 2021 Did some further testing, and it seems to work fine for most ROM's. Even mixing up different sizes works for some ROM's. Let me know if someone is interested, then I will share the Gerber files for PCB making... Quote Link to comment Share on other sites More sharing options...
cbelcher Posted November 12, 2021 Share Posted November 12, 2021 Interested! Quote Link to comment Share on other sites More sharing options...
SkalTura Posted November 14, 2021 Author Share Posted November 14, 2021 On 11/12/2021 at 5:38 PM, cbelcher said: Interested! Cool ;-) Here are the Gerber files. Also made a short video on YouTube, so you can see it working. Note: Only tested with a few games (because my machine is PAL, and most of the games I downloaded are NTSC), but it seems to work fine for the ones I used for testing... Quote Link to comment Share on other sites More sharing options...
cbelcher Posted November 14, 2021 Share Posted November 14, 2021 Ok and burn the desired F4 F6 or F8 GAL file from http://www.grandideastudio.com/pixels-past/ Correct? You said if there is no bankswitching the PLD is only used for CE chip enable - does it matter which file is used? Quote Link to comment Share on other sites More sharing options...
SkalTura Posted November 15, 2021 Author Share Posted November 15, 2021 (edited) 8 hours ago, cbelcher said: Ok and burn the desired F4 F6 or F8 GAL file from http://www.grandideastudio.com/pixels-past/ Correct? You said if there is no bankswitching the PLD is only used for CE chip enable - does it matter which file is used? Yes, use the PLD/GAL file from PixelPast. If you play only 4k games (for 2k games, double them), you only need the CE signal from the PLD, so then it doesn't matter what file you use, since the A12, A13 and A14 lines (sideways jumpers F8, F6 and F4) will be jumpered to either +5v or GND, and not to the PLD anymore. And you don't have to use a 1M Eeprom, you can also use a 27C256 or 27C512 is you have hem. Just place it as marked on the silkscreen... Edited November 15, 2021 by SkalTura Quote Link to comment Share on other sites More sharing options...
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