Penalty for not following exit sequence from high voltage programming mode on PIC18FxxKxx series
I have been working on a technique to recover flash memory contents from a locked PIC18F25K20 microcontroller.
To achieve this I am using an FTDI cable in bit-bang mode, and using my own code on a PC to act as an ICSP programmer. I am using the high voltage mode, as it is available even when the microcontroller is locked.
I have been manually connecting and disconnecting the Vpp voltage (8.5V), and I have not always followed the correct "exit sequence" as per the datasheet. Specifically, I have left Vpp connected whilst Vdd drops.
An extract of the entry and exit sequences are shown in this image:
The full document (PIC18F2XK20/4XK20 flash memory programming specification) is available here
During my experiments I have managed to put a couple of microcontrollers into a state where they still respond to ICSP commands but no longer work in a normal mode (i.e. run program code).
Could this be because I have not followed the exit sequence?
I have been working on a technique to recover flash memory contents from a locked PIC18F25K20 microcontroller.
To achieve this I am using an FTDI cable in bit-bang mode, and using my own code on a PC to act as an ICSP programmer. I am using the high voltage mode, as it is available even when the microcontroller is locked.
I have been manually connecting and disconnecting the Vpp voltage (8.5V), and I have not always followed the correct "exit sequence" as per the datasheet. Specifically, I have left Vpp connected whilst Vdd drops.
An extract of the entry and exit sequences are shown in this image:
The full document (PIC18F2XK20/4XK20 flash memory programming specification) is available here
During my experiments I have managed to put a couple of microcontrollers into a state where they still respond to ICSP commands but no longer work in a normal mode (i.e. run program code).
Could this be because I have not followed the exit sequence?
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