Atmel ARM-Based Evaluation Kit for SAM4S16C, 32-Bit ARM® Cortex® Microcontroller ATSAM4S-WPIR-RD ATSAM4S-WPIR-RD Data Sheet

SAM4S Series [DATASHEET]

Atmel-11100G-ATARM-SAM4S-Datasheet_27-May-14

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cycles. This corresponds respectively to about 100 µs, about 1 ms, about 16 ms, about 128 ms and about 1 

second (for a typical slow clock frequency of 32 kHz). Programming WKUPDBC to 0x0 selects an immediate 

wake-up, i.e., an enabled WKUP pin must be active according to its polarity during a minimum of one slow clock 

period to wake up the core power supply.
If an enabled WKUP pin is asserted for a time longer than the debouncing period, a wake-up of the core power 

supply is started and the signals, WKUP0 to WKUP15 as shown in 

, are latched in 

SUPC_SR. This allows the user to identify the source of the wake-up, however, if a new wake-up condition occurs, 

the primary information is lost. No new wake-up can be detected since the primary wake-up condition has 

disappeared.

Low-power debouncer inputs (WKUP0, WKUP1) can be used for tamper detection. If the tamper sensor is biased 

through a resistor and constantly driven by the power supply, this leads to power consumption as long as the 

tamper detection switch is in its active state. To prevent power consumption when the switch is in active state, the 

tamper sensor circuitry must be intermittently powered, and thus a specific waveform must be applied to the 

sensor circuitry.
The waveform is generated using RTCOUTx in all modes including backup mode. Refer to the RTC section for 

waveform generation.
Separate debouncers are embedded, one for WKUP0 input, one for WKUP1 input.
The WKUP0 and/or WKUP1 inputs perform a system wake-up upon tamper detection. This is enabled by setting 

the LPDBCEN0/1 bit in the 

 (SUPC_WUMR).

WKUP0 and/or WKUP1 inputs can also be used when VDDCORE is powered to detect a tamper.
When the bit LPDBCENx = 1, WKUPx pins must not be configured to act as a debouncing source for the 

WKUPDBC counter (WKUPENx must be cleared in SUPC_WUIR).
Low-power tamper detection or debounce requires RTC output (RTCOUTx) to be configured to generate a duty 

cycle programmable pulse (i.e., OUT0 = 0x7 in RTC_MR) in order to create the sampling points of both 

debouncers. The sampling point is the falling edge of the RTCOUTx waveform.

 shows an example of an application where two tamper switches are used. RTCOUTx powers the 

external pull-up used by the tamper sensor circuitry.

MCU

WKUP0

WKUP1

RTCOUTx

Pull-up
Resistor

Pull-up
Resistor

GND

GND

GND