Got my Star Wars with ESB Kit Storing Settings for both ESB and SW!

Altan

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Got my Star Wars with ESB Kit Storing Settings for both ESB and SW!

I've been digging into this for a couple of weeks and thought I'd share my story.

The problem my Star Wars game exhibited was that Star Wars would save high scores and settings as long as I never switched to Empire Strikes Back. Even if I always switched to ESB while the game was powered off, after playing ESB and switching back to Star Wars (with the power off), the Star Wars settings would be lost. Interestingly enough, however, running Star Wars didn't seem to corrupt the ESB settings.

I learned some interest tidbits by reading the "Schematic Package Supplement to Star Wars", using MAME and adding special diagnostic code to the x2212 logic, as well as examining the ESB daughter card.

Tidbit #1: The x2212 chip can write to persistent memory even when the chip select is not active

Tidbit #2: The ESB daughter card connects all pins from both x2212 chips together except for the chip select

While the ESB kit has special logic to ensure that the chip select for Star Wars's x2212 is only active if the game is set to Star Wars mode, because all the other pins are tied together the x2212 store operation is always performed on BOTH x2212 chips. Put another way, whenever Star Wars writes to persistent memory, the ESB x2212 chip is also told to write to persistent memory (even though that game isn't being played).

Tidbit #3: The Atari Hardware causes a x2212 store operation when you remove the power

Who typically thinks that hardware can do something when it is powered off? I really mean turning off the power switch or even pulling the AC plug from the wall! It means that individual actions that effect persistent data, such getting a top 3 high score in Star Wars, does not immediately consume a x2212 store cycle. The "store" only happens when you remove AC power --- which is really the only time it is ever needed!

I designed a small circuit that ensures the Star Wars x2212 "store" only occurs when Star Wars is active. Similarly, this circuit ensures that an Empire Strikes Back x2212 "store" only occurs when ESB is running. If nothing else, this will help with the lifespan of the x2212 chips as only one will perform a "store" at a time.

DSC_1317.jpg


In addition to my "store" enhancement above, I added a missing cap to my Star Wars board. The schematic indicates that C94 should be a 4.7 uF cap. For some reason, my Star Wars board didn't have this capacitor.

With these two changes, persistent storage for both Star Wars and Empire Strikes Back is working great!

(the above is a shorter version of the text I just wrote on my web site. If you want to see the longer text and a couple more pictures, check out my star wars page).

I hope this is helpful and/or interesting to someone out there with a Star Wars.

... Altan
 
My Star Wars/ESB kit has had this problem for some time now. Could you please, please do a writeup on how to build this circuit and connect it to the kit?
 
And the mystery of the cowgill sw/esb kit is finally solved. I think many people have changed out the x2212 chips thinking that was the problem and it didn't help.
 
good stuff :)

Nice work

Thanks!

TRONFREAK said:
And the mystery of the cowgill sw/esb kit is finally solved...

For the people that had trouble with Clay's kit, I suspect there are many different reasons --- mostly centering on various revisions of the Star Wars PCB as well as aged parts that behave differently from PCB to PCB. It's not clear to me how helpful my solution will be to others in general. Although I'm pretty sure it will cause your x2212s to last longer.

mjenison said:
My Star Wars/ESB kit has had this problem for some time now. Could you please, please do a writeup on how to build this circuit and connect it to the kit?

Tonight I added more details regarding the circuit design to my web site. It's really very simple. Let me know if you have questions. Still, it's important to note what I wrote to TRONFREK above. I really have no idea if this will help your Star Wars. You could do more damage if you attempt this and don't know what you are doing...

... Altan
 
Quick update... After a week or so, novram / persistent settings still working great. No data loss. :)

... Altan
 
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