Write protected PROMS

[Guest]

Greetings,

To test my s4 I read in the contents of a PROM that I had. I then wrote the same data straight back to the PROM. No probs. Next I changed a couple of bytes in the s4's RAM and tries to burn the PROM again. This time it failed on the bytes that I had changed.

This happened with two different PROMS (different makes of PROM) so I know the s4 isn't to blame.

These proms were lifted from a couple of P.C motherboards. Could they have some kind of write protection on them? Does this kind of thing exist?

Both PROMS reported "WILL BURN" when tested before burning.

I guess that the s4's write algorithm doesn't burn bytes that match in the ROM & RAM (to save time). This is why the straight read then write worked but the modified RAM bytes failed. Is this correct?

Any ideas anyone?

[Dataman (Neil Parker)]

Hi Anonymous,

When the S4 reports WILL BURN it basically means that the device is OK as in it can be burnt, but also that the device has data on it. The S4 can only write to a device if it is blank it cannot edit the data. If you try a FUNC BURN on the device it will attempt to erase it, then you will be able to burn data to it.
One other point to note is that when WILL BURN is displayed it is possible to burn aditional data to areas that are currently blank, you just cant change existing data.

Neil