900844 datasheet(49/118 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

900844

FUNCTIONAL DEVICE OPERATION

CLOCK GENERATION AND REAL TIME CLOCK (RTC)

AIE

Alarm Interrupt Enable

x0 = Alarm flag (AF) bit in Register C is not permitted to assert the interrupt request flag (IRQF) in Register C

x1 = Alarm flag (AF) bit in Register C is permitted to assert the interrupt request flag (IRQF) in Register C

Reserved

Fixed to 0

SET

Set mode enable bit for the program to initialize the time and calendar bytes

x0 = The update cycle functions normally by advancing the counts once-per-second.

x1 = Any update cycle in progress is aborted and the program may initialize the time and calendar bytes without an

update occurring in the midst of initializing.

RTCC (ADDR 0x1C - R - Default Value: 0x00)

Reserved

3:0

Reserved

Update-Ended Interrupt Flag. Set after each update cycle.

X0 = UIE bit will not effect IRQF state

x1 = When UIE bit goes high, the IRQF bit goes high

Alarm Interrupt Flag. Indicates that the current time has matched the alarm time.

X0 = AIE bit will not effect IRQF state

x1 = When AIE bit goes high, the IRQF bit goes high

Reserved

Fixed to 0

IRQF

Interrupt Request Flag. IRQF = (AF&AIE) + (UF&UIE)

The interrupt request flag (IRQF) is set to a “1” when one or more of the following are true:

AF = AIE = “1”

UF = UIE = “1”

x0 = Above Equation is not true

x1 = Above Equation is true

RTCD (ADDR 0x1D - R - Default Value: 0x00)

Reserved

6:0

Fixed to 000000

VRT

The Valid RAM and Time (VRT) bit indicates the condition of the contents of the RTC time and calendar registers.

A "0" appears in the VRT bit when the RTC registers have been reset. The processor program should set the VRT

bit after the time and calendar are initialized to indicate that the time and calendar are valid. The VRT bit can only

be set by reading register D.

RTCE (ADDR 0x1E - R/W - Default Value: 0x05)

OSCSTP

Oscillator (32 kHz) Clock Stop Flag

x0 = XTAL Oscillator

x1 = Internal RC Oscillator

BKDET

Coin Cell Backup Voltage Status

x0 = No change

x1 = Coin Cell below "low-voltage" threshold

When this bit is set to 1, the SW takes corresponding action for a coin cell well below the operating voltage, and

clears the BKDET to get ready for the next event.

POR

RTC Reset Flag

x0 = No reset was detected

x1 = POR occurred

SCRATCH

7:3

These bits shall not exert any control over the operation of the RTC, and are intended to be used as scratch pad

registers by the system controller. Their contents are erased on RTCPORB.

Table 20. RTC Control Registers Structure and Bit Description

Name

Bits

Description

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