Re: Reading a PAL fusemap with a microscope

On 16 Sep 2005 13:52:05 -0700, "logjam" <grant@xxxxxxxxxxxx> wrote:
>I posted this in another thread, but didn't hear from anyone. Maybe
>here it will get more exposure?

Probably not. We all read the same news group and articles.

>I'm beginning to question the organization of the fuse map in a HAL.
>It doesn't seem to be related to the datasheets. I've collected a lot
>of data so far and have outlined it below.

You do seem to be having too much fun. Considering the performance
of todays PCs, it would seem you could get to a solution by doing
an exhaustive search with a PC controlling the device via some simple
circuitry hanging of a printer port.

It seems you have hung much of your analysis on the assumption that
the chip layout should follow the diagrams in the data book.
There is no such requirement, and it would surprise me if you did
find a perfect match. The diagram in the data book is laid out
for easy of viewing and presenting a logical view of the functionality
of the device. The chip layout is laid out to minimize area,
to leverage repeated structures, to meet power/noise/other requirements.

For example, in the data *** you see the FF feedback coming
across the fuse array as two adjacent lines. But if the Q and Q-bar
outputs were not adjacent as they come out of the FF structure, then
on the chip the lines may not be adjacent. It is also very common to
see structures that share something are laid out as alternating
normal lay out and then mirrored layout, so that the shared
resource (a signal line, a power/ground, a control line) is only
needed once per pair of things.

>Can anyone give me any insight? Will I have to translate the location
>of the vertical fuse columns to what they "should be" in a GAL?

Hope the above helps expand what you are looking for. I still think
that a PC based sw/hw exploration would get you to a complete picture
with a few days of programming (changes as you learn stuff), and probably
less than an hour of CPU time.

FYI: The HAL products were promoted as Hard Array Logic, with the intent
of mask programming the devices for high volume cost reduction. In fact
many HAL devices were just normal PALs that were programmed at the
factory. Have you plugged the device into a PAL programmer and seen if
it can be read back? I hope so.

>Thanks,
>Grant

Philip Freidin
MMI FAE 1980-1983

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