Flash erase problems with P89C669

[Markus Heider]

Hello,

at the moment we have problems with using the IAP/ISP function ERASE FLASH BLOCK with the
P89C669.

I have studied the philips MCU forum as well as the forum at esacademy and I have found nothing
regarding our problem.
For that I post this questions both to philips MCU forum and esacademy forum.

In our application we are forced to implement the IAP function because our device has to be able
to be update via a remote modem connection and therefore the self implemented flashloader has to do
the hex-download and the modem initialisation and so on.

When the flashloader (located at block 0 (0x0000 to 0x1FFF)) receives the first valid hex record, the loader first
erases the blocks 1 to 7 (0x2000 to 0xFFFF); the memory beyond 0xFFFF is not used at the moment.
The erasing of a block is done with a call to 0xFFF0 with R1 = 0x0C.

The problem is, that the return value of the ERASE BLOCK command often reports a NOK.

We found out, that this problem
is dependent from supply voltage!!!
With VCC = 5.0 V this problem happens sometimes.
With VCC = 4.5 V this problem happens even more!
With VCC = 5.5 V this problem happens no more; all block erases are done without any error!!!!

So, our application (and I think the most other applications) can