Re: Reading a PAL fusemap with a microscope

Gabor is correct.

PAL's are programmed by blowing fuses or storing injecting charge like a
flash device. You can get factory programmed PAL's but they are still PAL's
and are no different than the ones you buy. Programming is a relatively
expensive process.

HAL's are 'Hard Array Logic'. They are programmed with a mask (the final,
metal mask) during manufacturing. They are generally ordered only in large
volume because the cost of the mask, testing and marking must be spread over
the end volume. Also, sometimes they can be made on smaller die, though for
the case of a 16X8 I doubt anyone bothers today.

Marc Reinig
System Solutions

"Gabor" <gabor@xxxxxxxxxxx> wrote in message
news:1126617095.796923.239650@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> logjam wrote:
>> I've had success reading the fuse map! :) It took 200x and a decent
>> microscope. Still holding the cheap digital camera to the eye piece,
>> but hey...it works. :)
>>
>> You can see in the images below that a HAL has all the fuses, but some
>> have been cut. So my guess would be rather than them being
>> manufactured with a pattern, they are manufactured 100% connected and
>> then mechanically cut later?
>
> I was under the impression that HALs were chaper than PALs. Therefore
> it would be unlikely that such a process would be used. While the
> gap at the "blown fuse" is small, it does not look significantly
> different than other gaps in the metalization pattern. I think
> a mechanical process would have left some sort of recognizable
> "scar" at the cut. The other method used commonly to remove
> metalization, "laser trimming", would also leave some visible
> mark.
>
> More likely the HAL started from the same mask set as the PAL, but
> the cuts were added to the mask. Also it is likely that to save
> more on processing, the "fuse" metallization is actually the
> standard aluminum used in the rest of the chip rather than the
> alloys used for a fusible link. All of the cuts would be in
> a single mask layer, allowing the factory to pre-build most of
> the chip and do quick turns for new patterns.
>
> Just my 2 cents,
> Gabor
>


.

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