ATA6612C View Datasheet(PDF) - Atmel Corporation
Part Name
Description
MFG CO.
ATA6612C
Atmel Corporation
'ATA6612C' PDF : 312 Pages View PDF
5.8 System Control and Reset
5.8.1
Resetting the AVR
During reset, all I/O registers are set to their initial values, and the program starts execution from the reset vector. For the
Atmel® ATA6613C, the instruction placed at the reset vector must be a JMP – absolute jump – instruction to the reset
handling routine. For the Atmel ATA6612C, the instruction placed at the reset vector must be an RJMP – relative jump –
instruction to the reset handling routine. If the program never enables an interrupt source, the interrupt vectors are not used,
and regular program code can be placed at these locations. This is also the case if the reset vector is in the application
section while the interrupt vectors are in the boot section or vice versa (Atmel ATA6612C/ATA6613C only). The circuit
diagram in Figure 5-15 on page 61 shows the reset logic. Table 5-20 on page 62 defines the electrical parameters of the
reset circuitry.
The I/O ports of the AVR® are immediately reset to their initial state when a reset source goes active. This does not require
any clock source to be running.
After all reset sources have gone inactive, a delay counter is invoked, stretching the internal reset. This allows the power to
reach a stable level before normal operation starts. The time-out period of the delay counter is defined by the user through
the SUT and CKSEL fuses. The different selections for the delay period are presented in
Section 5.6.2 “Clock Sources” on page 47.
5.8.2
Reset Sources
The Atmel ATA6612C/ATA6613C has four sources of reset:
● Power-on reset: The MCU is reset when the supply voltage is below the power-on reset threshold (VPOT).
● External reset: The MCU is reset when a low level is present on the RESET pin for longer than the minimum pulse
length.
● Watchdog system reset: The MCU is reset when the watchdog timer period expires and the watchdog system reset
mode is enabled.
● Brown-out reset: The MCU is reset when the supply voltage VCC is below the brown-out reset threshold (VBOT) and the
brown-out detector is enabled.
60 ATA6612C/ATA6613C [DATASHEET]
9111L–AUTO–11/14
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