14.3.1RTC Status and Control Register (RTCSC)

RTCSC contains the real-time interrupt status flag (RTIF), the clock select bits (RTCLKS), the real-time interrupt enable bit (RTIE), and the prescaler select bits (RTCPS).

R

W

Reset:

7

6

5

4

3

2

1

0

RTIF

RTCLKS

 

RTIE

 

 

RTCPS

 

 

 

 

 

 

 

 

 

0

0

0

0

0

0

0

0

 

 

 

 

 

 

 

 

 

 

Figure 14-2. RTC Status and Control Register (RTCSC)

 

 

Table 14-2. RTCSC Field Descriptions

 

 

 

Field

 

Description

 

 

7

Real-Time Interrupt Flag This status bit indicates the RTC counter register reached the value in the RTC modulo

RTIF

register. Writing a logic 0 has no effect. Writing a logic 1 clears the bit and the real-time interrupt request. Reset

 

clears RTIF.

 

0

RTC counter has not reached the value in the RTC modulo register.

 

1

RTC counter has reached the value in the RTC modulo register.

 

 

65

Real-Time Clock Source Select. These two read/write bits select the clock source input to the RTC prescaler.

RTCLKS

Changing the clock source clears the prescaler and RTCCNT counters. When selecting a clock source, ensure

 

that the clock source is properly enabled (if applicable) to ensure correct operation of the RTC. Reset clears

 

RTCLKS.

 

00 Real-time clock source is the 1-kHz low power oscillator (LPO)

 

01 Real-time clock source is the external clock (ERCLK)

 

1x Real-time clock source is the internal clock (IRCLK)

 

 

4

Real-Time Interrupt Enable. This read/write bit enables real-time interrupts. If RTIE is set, then an interrupt is

RTIE

generated when RTIF is set. Reset clears RTIE.

 

0 Real-time interrupt requests are disabled. Use software polling.

 

1

Real-time interrupt requests are enabled.

 

 

3–0

Real-Time Clock Prescaler Select. These four read/write bits select binary-based or decimal-based divide-by

RTCPS

values for the clock source. See Table 14-3. Changing the prescaler value clears the prescaler and RTCCNT

 

counters. Reset clears RTCPS.

 

 

 

Table 14-3. RTC Prescaler Divide-by values

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RTCPS

 

 

 

 

 

 

 

 

 

 

 

 

 

RTCLKS[0]

0

 

1

 

2

 

3

 

4

 

5

 

6

 

7

 

8

 

9

 

10

 

11

 

12

 

13

 

14

 

15

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

Off

 

23

 

25

 

26

 

27

 

28

 

29

 

210

 

1

 

2

 

22

 

10

 

24

 

102

 

5x102

 

103

1

Off

 

210

 

211

 

212

 

213

 

214

 

215

 

216

 

103

 

2x103

 

5x103

 

104

 

2x104

 

5x104

 

105

 

2x105

MCF51QE128 MCU Series Reference Manual, Rev. 3

286

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Freescale Semiconductor MCF51QE128RM RTC Status and Control Register Rtcsc, Rtcsc Field Descriptions, Rtif, Rtcps RTCLKS0