AT91SAM7L64 ATMEL Corporation, AT91SAM7L64 Datasheet - Page 31

• Manufacturer Part Number: AT91SAM7L64
• Description: (AT91SAM7L64 / AT91SAM7L128) AT91 ARM Thumb-based Microcontroller
• Manufacturer: ATMEL Corporation

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9.2
9.3
9.3.1
6257AS–ATARM–28-Feb-08
Supply Controller (SUPC)
Reset Controller
Brownout Detector (BOD) and Power-on Reset
The Supply Controller controls the power supplies of each section of the product:
The Supply Controller has its own reset circuitry and is clocked by the 32 kHz Slow clock
generator.
The reset circuitry is based on the NRSTB pin, a zero-power power-on reset cell and a brownout
detector cell. The zero-power power-on reset allows the Supply Controller to start properly, while
the software-programmable brownout detector allows detection of either a battery discharge or
main voltage loss.
The Slow Clock generator is based on a 32 kHz crystal oscillator and an embedded 32 kHz RC
oscillator. The Slow Clock defaults to the RC oscillator, but the software can enable the crystal
oscillator and select it as the Slow Clock source.
The Supply Controller starts up the device by sequentially enabling the internal power switches
and the Voltage Regulator, then it generates the proper reset signals to the core power supply.
It also enables to set the system in different low power modes and to wake it up from a wide
range of events.
The AT91SAM7L128/64 embeds one zero-power power-on reset and a brownout detection cir-
cuit. Both monitor VDDIO1.
The zero-power power-on reset circuit is always active. It provides an internal reset signal to the
AT91SAM7L128/64 for power-on and power-off operations and ensures a proper reset for the
Supply Controller.
The brownout detection circuit is disabled by default and can be enabled by software. It monitors
VDDIO1.
The brownout detection circuit is factory calibrated.
The threshold is programmable via software. It can be selected from 1.9V to 3.4V with 100 mV
steps. It can be programmed to generate either a wake-up alarm or a reset.
It can be used to wake up the chip from backup mode if the supply drops below a selected
threshold (to warn the end user about a discharged battery for example) and to reset the chip
when the voltage is too low.
• the processor and the peripherals
• the Flash memory
• the backup SRAM
• the LCD controller, the charge pump and the LCD voltage regulator
• the Real Time Clock
• Based on one power-on reset cell and a brownout detector
• Status of the last reset; either power-up reset, software reset, user reset, watchdog reset,
• Controls the internal resets and the NRST pin output
• Allows to shape a signal on the NRST line, guaranteeing that the length of the pulse meets
brownout reset
any requirement.
AT91SAM7L128/64 Preliminary
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