A 91 KB PDF datasheet covering the AT89C51, the Atmel 8051-compatible microcontroller with flash program memory that turns up in many older industrial and consumer control boards. Inside you can expect the pin assignment, electrical characteristics, memory organisation and the programming and verify procedure. Repair work typically means checking VCC, reset and crystal oscillation against the documented values, and comparing the marking and package on the board with the datasheet before swapping the chip or reprogramming it in a universal programmer.
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