Datasheet

2
4257D–8051–04/04
6. Boot Process - Upper 2Kbytes Execution with BLJB = 0
In case of Boot process with BLJB = 0 and BSB = 00, the User Application is executed but the program space located
in the upper 2KBytes of the 64KBytes on chip Flash memory cannot be executed. This is due to ENBOOT bit which is
set in this Bootloader flow.
Workaround
Clear ENBOOT bit at the beginning of user application software.