GAL20V8

[PhilArqiva]

Unfortunately our company still uses GAL chips in some telemetry equipment. The chips are being used in an I/O card in between the processor card and the main I/O chips. The problem we have is that something happens with a particular GAL chip, it seems to have failed by stopping the CPU from booting up. I can take known working chip, copy it into another chip of the same type and the chip won't work, the two chips verify okay, I can take another faulty chip without blanking it, it will verify okay against working chip. The GAL chips being used are Latice GAL20V8A and NS GAL20V8, we cannot get any of these to work, even though they verify okay. Unfortunately we only have a working chip as our source code and to verify against, this may be the problem, or I am doing something wrong with the programmer. We are using a Dataman 448pro programmer. What am I doing wrong, any ideas?

[Dataman (Neil Parker)]

Hello PhilArqiva,

Both of these chips have a security fuse, therefore if set, the read procedure will only get invalid data from the chip.

Are you sure these devices are not read-protected?

[PhilArqiva]

Thank you for getting back to me. How would you know whether a device has had the security bits enabled using a dataman programmer?

[Dataman (Neil Parker)]

Hello PhilArqiva,

After READing a protected device the buffer content will usually be all FFh or 00h.

[PhilArqiva]

Hi Neil

We don't get that, we see what looks like a HEX file back from the chip. We have also tried different manufacturers of the GALs too, we get different check sums, but I suppose that's because the different chips have different algorithm's to program them.

Many thanks

[dorkshoei1]

Hello PhilArqiva,

After READing a protected device the buffer content will usually be all FFh or 00h.

Sorry to threadjack but I'm trying to program a GAL20V8 using a Dataman 48pro.

There are two checkbox options at programming time.

[X] Device without security fuse
[ ] Security fuse

Can you clarify the purpose of two options as they seem mutually exclusive.

I left as above and now the device reads all 1s and I cannot erase it.

[Dataman (Neil Parker)]

Hello dorkshoei1,

The first checkbox will program only the main logic array and the UES area but it will not protect the device by setting the security fuse. If you wish to secure the device after programming the main logic array, you would also need to select the security fuse checkbox.

According to the datasheet for this device the erase procedure will clear the entire logic array, including the UES and security bit allowing the reprogramming of the device.

If you have any further questions, please do not hesitatat to conatct us.

[dorkshoei1]

Well then there seems to be a problem.

I have a PAL20L8 which I read as a PAL20L8.

I wanted to program a replacement using a GAL20V8 which according to the device datasheet it can emulate.

I selected device "GAL20V8 as PAL20L8". I left the checkboxes as default, which based on your explanation should have only programmed the main logic and UES. However I am now unable to erase the device. If I try I get a manufacturer/device check error but both are FFh.

So what happens if I deselect both checkboxes? There are two separate checkboxes so that's 4 possible permutations which doesn't make sense to me.

[Dataman (Neil Parker)]

Hello dorkshoei1,

Does your PAL20L8 chip have a manufacturer, can you specify?
What GAL20V8 do you have? I need to know the manufacturer?
How was this "PAL20L8" read? By what programmer?
Which "GAL20V8 as PAL20L8" selection did you use - I can see a few such selections in our software.

[dorkshoei1]

First. Can you answer my question on the meaning of the two check boxes.

Again I see as default for all GAL20* devices:

[X] Device without security fuse
[ ] Security fuse

I can deselect the former and have:

[ ] Device without security fuse
[ ] Security fuse

I have no idea what this second form means and I don't want to "just try it" and mess up a second device. I can't find any documentation in "device info" or in the manual. As I said earlier two independent check boxes implies to me 4 distinct permutations.

To answer your question.

The GAL is a Lattice GAL20V8B-25LP.

The PAL was a TI TIBPAL20L8-25

I programmed using "LATTICE GAL20V8B as PAL20L8". I couldn't find any documentation in "device info" or the manual on these "as" operations but I chose it as my assumption was that the JEDEC file read from the TI PAL required transformation before it could be programmed onto the Lattice GAL and this "as" operation would perform this transformation.

I'd like to test program a GAL using device "LATTICE GAL20V8B" (no "as") but as I said I'm still confused over the meaning of these two checkboxes and don't want to brick another chip.

Thanks for the help!