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Thread: A vs W head compatabiltiy

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    Default A vs W head compatabiltiy

    Hey guys. Just something neat i wanted to share with you. I think we all already knew that we could rechip a A9 into a W9, by changing out the eproms. I was always suspectful that similar was possible with the W4, 5, and 7 series. So I got a W4 from a friend the other day, had a problem with the display high voltage, and was proving to be just a pain in the rear to try and repair. So, I took U1 off of it, and replanted U1 on an A4. As I suspected, it turned the A4 into a W4. Very cool, and was fully functional. I think the same probably applies the the W5/7 series heads as well. So, hang on to those old A series heads, good source of parts.

    Randy


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    I theorized the same thing, the microcontrollers on the w4 w5 w7 heads have an internal rom with the firmware. So swapping these chips is just like exchanging the rom on the bigger head.

    It would be nice to have the firmware in case these chips are still available for programming

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    true a dump of the chip might be usefull for simple hardware conversions

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    4n6inv No Longer Registered

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    Been discussing it in another thread. The chips are available, but not dirt cheap. Not off the chart, either. The problem is finding a READER / PROGRAMMER!!! And; assuming that Motorola didn't secure the chip from prying eyes - as is usually done. I've been trying to smoke this one out for several years. Perhaps; this thread may rekindle some interested parties aside from myself. I have TONS of "A" series heads. I just need about 20-25 "dead" "W" donor boards. replacing the PLCC chip is mothers milk to me.

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    We might be able to dump the W chip in-situ. I wrote some special tools to do this on earlier heads and I have a W7 head here. I should also have a W4. It's going to be a few days before I can dig them out but I'll try it.

    The programmer is not really difficult, the microcontroller is a usual 6805 or 6811.

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    I was always sure that the A4/W4 U1 chip replacement can be done but I have never had the proper tools to do it.

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    4n6inv No Longer Registered

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    The actual chip that I've seen in nearly every one is MC68HC705C8CFN. Although; on a select few of the "W" series, I've seen MC68HC705C8A. Check out the notes in the other thread https://www.p25.ca/threads/3384-W-3-HHCH-Help-Needed . It's also the same controller chip used in the W3 HHCH, and I've been itching to read the different ones I've seen to see what - if any differences there are. Check out the recent notes towards the end of the thread and see if you agree. Monkeyrola uses the same chip on several different boards besides control heads.

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    The one I found without cryptic code was a 68HC705C8A in an A7 head. Used to have the tools to do various 6800 controllers but passed them on thinking Id never need them again . Looking to see if anyone has a generic solution and found this http://www.midondesign.com/PROG05/PROG05.html but havnt looked it over enough to see if it will verify/read. Just not sure on the security bit, they set it as a matter of course or didnt set it because its a contol panel not a big piracy or security concern.

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    Unfortunately, they say they are no longer producing that item due to lack of interest. Too bad, but it does show the nature of the device, it is a self-programming MCU. There are no other components involved save an RS-232 level translator IC (MAX232 type). You can set up a circuit like theirs, which bootstraps the chip into programming mode and then uses the on-chip serial UART to download an S-Record.

    You can also set up a different programming circuit for it that directly downloads the internal EPROM of the '705 from a conventional 2k or 4k EPROM (2716 or 2732, IIRC) and it has similar programming switches that will boot the device into a self-programming mode and then it steps through the addresses and transfers whatever data is on the data bus lines into the internal EPROM of the MCU. That programming setup is what we used to use in the video game industry, and the circuit is documented in the Data Book Sheets for the '705.

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    Yea it looked simple enough and the SW is right there on the site might be worth a try if I get some time. About the only struggle for the junkbox would be a 2MC crystal.