Winbond W78IE52 Microcontroller Protected Eeprom Breaking

If we can figure out the root of W78IE52 booting it will be easier for us to locate the security fuse and disable it, furthermore it can help us to find the databus of MCU then through microprobing to get the program out. By default, the W78IE52 boots from APROM program after a power on reset. On some occasions, user can force the W78E62B to boot from the LDROM program via following settings.

The possible situation that you need to enter F04KBOOT mode is when the APROM program can not run properly and device can not jump back to LDROM to execute in-system programming function. Then you can use this F04KBOOT mode to force the W78IE52 jumps to LDROM and excutes in-system programming procedure.

F04KBOOT MODE

When you design your system, you may reserve the pins P2.6, P2.7 to switches or jumpers. For example in a CD-ROM system, you can connect the P2.6 and P2.7 to PLAY and EJECT buttons on the panel. When the APROM program fails to execute the normal application program.

User can press both two buttons at the same time and then turn on the power of the personal computer to force the W78IE52 to enter the F04KBOOT mode. After power on of personal computer, you can release both buttons and finish the in-system programming procedure to update the APROM code from Winbond W78IE52 Microcontroller Protected Eeprom Breaking.

In application system design, user must take care of the P2, P3, ALE, EA and PSEN pin value at reset to prevent from accidentally activating the programming mode or F04KBOOT mode.

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