Interrupt Driven; Typical System Implementation - Micro crystal RV-1805-C3 Applications Manual

Micro Crystal
Extrem Low Power Real Time Clock / Calendar Module RV-1805-C3
4.18.4.

INTERRUPT DRIVEN

The following Figure illustrates the simplest application, in which the RV-1805-C3 communicates with the system
MCU using an interrupt. The MCU can go into standby mode, reducing power somewhat, until the RV-1805-C3
generates an interrupt based on an alarm or a timer function. This produces smaller power savings than other
alternatives, but
allows the MCU to wake in the shortest time.
Interrupt Driven Power Control:
V V
2
DD DD
I C
RV-1805-C3
MCU
CLK / INT IRQ
V V
WDI
SS SS
4.19.

TYPICAL SYSTEM IMPLEMENTATION

The following Figure is a more detailed view of a typical system using the V Power Switched approach. The V
SS SS
pin of the MCU, and potentially other system components, is switched using the PSW pin of the RV-1805-C3. The
CLK / INT
pin of the RV-1805-C3 is connected to an interrupt input of the MCU, allowing the MCU to utilize the
RTC interrupt functions of the RV-1805-C3 when it is awake. The RST output of the RV-1805-C3 is connected to
the reset input of the MCU, enabling the RV-1805-C3 to control power on reset and integrate an external MCU
2
reset button RESET. The MCU controls the RV-1805-C3 over the I C channel.
System Example:
V V
2
DD DD
I C
RV-1805-C3
MCU
WDI RST
RST
CLK / INT INT
PSW
V
V
SS
SS
RESET or
WAKE
The key value of the RV-1805-C3 in this type of system is the ability to put the MCU into an off state, and providing
a very rich variety of triggers which can cause the RV-1805-C3 to wake the MCU from the off state. There are a
number of different triggers which may be useful.
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