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Reverse Engineering IC ATmega1284PV structure to locate the security fuse bit, by unlocking MCU ATmega1284 memory and readout ATmega1284 IC Firmware.

Timer/Counter0 is a general purpose 8-bit Timer/Counter module, with two independent Output Compare Units, and with PWM support. It allows accurate program execution timing (event management) and wave generation. The main features are:

Two Independent Output Compare Units

Double Buffered Output Compare Registers

Clear Timer on Compare Match (Auto Reload)

Glitch Free, Phase Correct Pulse Width Modulator (PWM)

Variable PWM Period

Frequency Generator

Three Independent Interrupt Sources (TOV0, OCF0A, and OCF0B)

A simplified block diagram of the 8-bit Timer/Counter is shown in Figure 38. For the actual placement of I/O pins, refer to “Pinout ATmega640/1280/2560” on page 2. CPU accessible I/O Registers, including I/O bits and I/O pins, are shown in bold. The device-specific I/O Register and bit locations are listed in the “8-bit Timer/Counter Register Description” on page 128.

The Timer/Counter (TCNT0) and Output Compare Registers (OCR0A and OCR0B) are 8-bit registers. Interrupt request (abbreviated to Int.Req. in the figure) signals are all visible in the Timer Interrupt Flag Register (TIFR0). All interrupts are individually masked with the Timer Interrupt Mask Register (TIMSK0). TIFR0 and TIMSK0 are not shown in the figure.

The Timer/Counter can be clocked internally, via the prescaler, or by an external clock source on the T0 pin. The Clock Select logic block controls which clock source and edge the Timer/Counter uses to increment (or decrement) its value when attack mcu pic16c558 program.

The Timer/Counter is inactive when no clock source is selected. The output from the Clock Select logic is referred to as the timer clock (clkT0).

The double buffered Output Compare Registers (OCR0A and OCR0B) are compared with the Timer/Counter value at all times. The result of the compare can be used by the Waveform Generator to generate a PWM or variable frequency output on the Output Compare pins (OC0A and OC0B). See “Output Compare Unit” on page 119. for details.

The Compare Match event will also set the Compare Flag (OCF0A or OCF0B) which can be used to generate an Output Compare interrupt request.