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 Post subject: Problem with AE29F1008
PostPosted: Tue Aug 14, 2018 6:00 am 
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Hi, I've made a repro with an AE29F1008 as the PRG ROM, wich I can't find the datasheet. :-(
The problem is that after falling, the connection of the /WE (or is it VPP?) pin just dropped.

The game isn't working and I suspect this loose connection could have triggered a write operation, wich after reading it's contents and comparing to the ROM written have the 2nd half different from what it should.

Could this be possible?
Anyone has the datasheet for this IC?
Thanks in advance.


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PostPosted: Tue Aug 14, 2018 1:28 pm 
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/WE pin HAS TO be connected to VCC, otherwise ROM might not return proper data.


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PostPosted: Tue Aug 14, 2018 1:32 pm 
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Sorry, I didn't mention I restored the Vcc connection and even with this the game didn't work.
Since half of the data (maybe a bit less) is corrupt, what could have made this?
Looks like I should do better connections, specially in this particular pin.


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PostPosted: Wed Aug 15, 2018 4:04 am 
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Interesting.
After reflashing the PRG, I dicovered some bad connections under the mapper, in this case, a DIP IC marked as MC-3.
Looks like it was a totally messed up combination of a damaged board + cheap soldering wire + a fall from about 1,20m.

This doesn't explains why the flash was corrupted.
Any ideas of where I can find this IC's datasheet or is it a knockoff of other well known IC?
Maybe I got these errors when reading? But the write operation was fine...
Anyway, thanks.


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PostPosted: Sat Aug 18, 2018 2:46 am 
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Quote:
Since half of the data (maybe a bit less) is corrupt

It reminds me reading memories like 27256 when programmer was set to 27512 - half of the memory was OK, while the other half was only FFs. That's because pin 1 in 27512 is A15 and in 27256 is VPP, so for the first half it was at 0.


I used similar memories (29EE010) in my Mapper 9 project (viewtopic.php?f=28&t=17496) and the game crashed ranomly, because !WE (or !P, whatever it is called) was connected to CPU_R/!W instead of VCC (because I wanted to be able to flash it using kazzo). Out of curiosity, reading from the memory using Kazzo worked, so it looked like game writes to mapper registers triggered some mode in ROM which prevented it from reading. Though, nothing in this flash memory was overwritten (it is not easy to make even one byte overwritten, because programming needs 4-5 write cycles with alternating AAAA/5555 on adress bus).

My general rule of thumb that always work is to assume that all address/data/control (!CE/!OE) lines in the 27/29 memory series (except 27801) is in the same place. So for your AE29F1008 I would assume that the pinout is like below.
All other unused pins (1, 32, 30) should be tied to VCC.


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PostPosted: Sat Aug 18, 2018 4:58 am 
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Thanks.
The information I was looking for was the write algorithm.
I probably have a problem with my programmer, wich is just an old motherboard.
I'll check it out.


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