Break IC, Recover MCU, Microcontroller Reverse Engineering

Archive for December, 2010

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When the SM2..0 bits are written to 010, the SLEEP instruction makes the MICROCONTROLLER enter Power-down mode. In this mode, the external Oscillator is stopped, while the external interrupts, the 2-wire Serial Interface, and the Watchdog continue operating (if enabled).

Only an External Reset, a Watchdog Reset, a Brown-out Reset, 2-wire Serial Interface address match, an external level interrupt on INT7:4, an external interrupt on INT3:0, or a pin change interrupt can wake up the MICROCONTROLLER. This sleep mode basically halts all generated clocks, allowing operation of asynchronous modules only if attack microcontroller pic18f66k90 heximal.

Note that if a level triggered interrupt is used for wake-up from Power-down mode, the changed level must be held for some time to wake up the MICROCONTROLLER. Refer to “External Interrupts” on page 75 for details.

When waking up from Power-down mode, there is a delay from the wake-up condition occurs until the wake-up becomes effective. This allows the clock to restart and become stable after having been stopped. The wake-up period is defined by the same CKSEL Fuses that define the Reset Time-out period, as described in “Clock Sources” on page 40.

When the SM2..0 bits are written to 011, the SLEEP instruction makes the MICROCONTROLLER enter Power-save mode. This mode is identical to Power-down, with one exception if copy PIC18F458 MICROCONTROLLER binary:

If Timer/Counter2 is enabled, it will keep running during sleep. The device can wake up from either Timer Overflow or Output Compare event from Timer/Counter2 if the corresponding Timer/Counter2 interrupt enable bits are set in TIMSK2, and the Global Interrupt Enable bit in SREG is set.

If Timer/Counter2 is not running, Power-down mode is recommended instead of Power-save mode.

The Timer/Counter2 can be clocked both synchronously and asynchronously in Power-save mode. If the Timer/Counter2 is not using the asynchronous clock, the Timer/Counter Oscillator is stopped during sleep. If the Timer/Counter2 is not using the synchronous clock, the clock source is stopped during sleep. Note that even if the synchronous clock is running in Power-save, this clock is only available for the Timer/Counter2.

When the SM2..0 bits are 110 and an external crystal/resonator clock option is selected, the SLEEP instruction makes the MICROCONTROLLER enter Standby mode. This mode is identical to Power-down with the exception that the Oscillator is kept running. From Standby mode, the device wakes up in six clock cycles after Break MICROCONTROLLER.

When the SM2..0 bits are 111 and an external crystal/resonator clock option is selected, the SLEEP instruction makes the MICROCONTROLLER enter Extended Standby mode. This mode is identical to Power-save mode with the exception that the Oscillator is kept running.

From Extended Standby mode, the device wakes up in six clock cycles. The Power Reduction Register, PRR, provides a method to stop the clock to individual peripherals to reduce power consumption. The current state of the peripheral is frozen and the I/O registers can not be read or written.

Resources used by the peripheral when stopping the clock will remain occupied, hence the peripheral should in most cases be disabled before stopping the clock. Waking up a module, which is done by clearing the bit in PRR, puts the module in the same state as before shutdown.

Module shutdown can be used in Idle mode and Active mode to significantly reduce the overall power consumption. See “Supply Current of IO modules” on page 381 for examples. In all other sleep modes, the clock is already stopped.

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These bits define the division factor between the selected clock source and the internal system clock. These bits can be written run-time to vary the clock frequency to suit the application requirements.

As the divider divides the master clock input to the MCU, the speed of all synchronous peripherals is reduced when a division factor is used. The division factors are given in Table 20.

The CKDIV8 Fuse determines the initial value of the CLKPS bits. If CKDIV8 is unprogrammed, the CLKPS bits will be reset to “0000”.

If CKDIV8 is programmed, CLKPS bits are reset to “0011”, giving a division factor of 8 at start up. This feature should be used if the selected clock source has a higher frequency than the maximum frequency of the device at the present operating conditions after Recover chip c8051f340 firmware.

Note that any value can be written to the CLKPS bits regardless of the CKDIV8 Fuse setting. The Application software must ensure that a sufficient division factor is chosen if the selected clock source has a higher frequency than the maximum frequency of the device at the present operating conditions. The device is shipped with the CKDIV8 Fuse programmed.

Sleep modes enable the application to shut down unused modules in the MCU, thereby saving power. The AVR provides various sleep modes allowing the user to tailor the power consumption to the application’s requirements after break mcu dspic30f4011 hex.

To enter any of the five sleep modes, the SE bit in SMCR must be written to logic one and a SLEEP instruction must be executed. The SM2, SM1, and SM0 bits in the SMCR Register select which sleep mode (Idle, ADC Noise Reduction, Power-down, Power- save, or Standby) will be activated by the SLEEP instruction

The MCU is then halted for four cycles in addition to the start-up time, executes the interrupt routine, and resumes execution from the instruction following SLEEP. The contents of the Register File and SRAM are unaltered when the device wakes up from sleep. If a reset occurs during sleep mode, the MCU wakes up and executes from the Reset Vector.