Hello Friends,

I have implemented Erik's back door for P89C51RD2BN a few weeks ago and it works neatly, I should have done this months ago and saved a lot of headaches!

I am now trying to implement it for the P89C669FA which is slightly different.

I have pasted the following from the Philips user manual for the 89C669:

PROGRAM SPECIAL CELL
Input Parameters:

R1 = 06h

EPL = 00h = program status byte
01h = program boot vector 0
02h = program boot vector 1
03h = reserved
04h = program config

ACC = byte to program


Could someone please tell me which is the BVH (boot vector high) and which is the BVM (boot vector middle),that is whether boot vector 0 (01h) is BVH or BVM.


Regards,
John.