AN2476 datasheet(24/49 Pages) STMICROELECTRONICS

24 / 49 page

Power supply and clocks

AN2476

24/49

The RTC can wake-up the MCU from STANDBY mode at each RTC alarm event,

independently from external interrupt line #15 (no need to configure it). Note that the RTC

Second or Overflow interrupts do not wake-up the MCU from STANDBY.

The condition which wakes-up the MCU from STANDBY is a rising edge of the output of an

OR gate between the P1.15 input pin and the RTC alarm event, see Figure 11: Internal

connections of the external interrupt line #15 on page 24.

Consequently, to wake-up from STANDBY by an RTC alarm, you must:

●

Apply low level to P1.15 pin.

●

Configure the RTC to generate the RTC alarm.

Figure 11.

Internal connections of the external interrupt line #15

Wake-up latency

The latency is the same as when resuming from reset.

I/O states in STANDBY mode

In STANDBY mode, all GPIOs are configured in high impedance except the WKP_STDBY

pin which is kept in input mode.

All other pins are disabled (XT1, XT2, XRTC1/2, USB, etc.) except the NRSTIN and

NRSTOUT pins which are still functional.

Debug mode

If using the debug features of the ARM7TDMI-S, and the current application puts the MCU

in STANDBY mode, the debug connection will be lost, because the ARM7TDMI-S core is no

longer powered.

RTC

powered in STANDBY

P1.15 (WKP_STDBY)

RTC_ALARM

CK_RTC

WKP_STDBY

EXTERNAL

INTERRUPT

CONTROLLER

LINE 15

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