Datasheet for the ATmega128A AVR microcontroller, a 2.68 MB PDF. The A suffix denotes the revised version of the ATmega128, and the document covers its 64-pin pinout, memory, peripherals, JTAG, fuse bits and electrical characteristics. Technicians use it to locate power, reset, crystal and programming pins on dense boards and to set fuses correctly when reflashing. Check the chip marking, since the original ATmega128 compatibility fuse and related settings affect behaviour after programming.
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