ST72561K6-Auto datasheet(89/324 Pages) STMICROELECTRONICS

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ST72561-Auto

Main clock controller with real time clock MCC/RTC

Doc ID 12370 Rev 8

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Main clock controller with real time clock MCC/RTC

The Main Clock Controller consists of three different functions:

●

a programmable CPU clock prescaler

●

a clock-out signal to supply external devices

●

a real time clock timer with interrupt capability

Each function can be used independently and simultaneously.

10.1

Programmable CPU clock prescaler

The programmable CPU clock prescaler supplies the clock for the ST7 CPU and its internal

peripherals. It manages SLOW power saving mode (See Section 7.2: Slow mode for more

details).

The prescaler selects the fCPU main clock frequency and is controlled by three bits in the

MCCSR register: CP[1:0] and SMS.

10.2

Clock-out capability

The clock-out capability is an alternate function of an I/O port pin that outputs a fOSC2 clock

to drive external devices. It is controlled by the MCO bit in the MCCSR register.

10.3

Real time clock timer (RTC)

The counter of the real time clock timer allows an interrupt to be generated based on an

accurate real time clock. Four different time bases depending directly on fOSC2 are available.

The whole functionality is controlled by 4 bits of the MCCSR register: TB[1:0], OIE and OIF.

When the RTC interrupt is enabled (OIE bit set), the ST7 enters ACTIVE HALT mode when

the HALT instruction is executed. See Section 7.5: Active halt mode for more details.

Figure 38.

Main clock controller (MCC/RTC) block diagram

DIV 2, 4, 8, 16

MCC/RTC INTERRUPT

SMS

CP1 CP0

TB1

TB0

OIE

OIF

CPU CLOCK

MCCSR

RTC

COUNTER

TO CPU AND

PERIPHERALS

fOSC2

fCPU

MCO

WATCHDOG

TIMER

ST72561K6-Auto Datasheet(PDF) 89 Page - STMicroelectronics

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