Rtc Status And Control Register (Rtcsc) - ROHS MC9S08QE128 Reference Manual

Real-Time Counter (S08RTCV1)
13.3.1

RTC 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).
7
R
RTIF
W
Reset: 0
Field
7 Real-Time Interrupt Flag — This status bit indicates the RTC counter register reached the value in the RTC
RTIF modulo register. Writing a logic 0 has no effect. Writing a logic 1 clears the bit and the real-time interrupt request.
Reset clears RTIF to 0.
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.
6:5 Real-Time Clock Source Select — These two read/write bits select the clock source input to the RTC
RTCLKS prescaler. 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 to 00.
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
RTIE is generated when RTIF is set. Reset clears RTIE to 0.
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
RTCPS divide-by values for the clock source. See
RTCCNT counters. Reset clears RTCPS to 0000.
RTCLKS[0]
0 1
3
0 OFF 2
10
1 OFF 2
242
6 5
RTCLKS
0 0
Figure 13-3. RTC Status and Control Register (RTCSC)
Table 13-2. RTCSC Field Descriptions
Table 13-3. RTC Prescaler Divide-by values
2 3 4 5
5 6 7 8
2 2 2 2
11 12 13 14
2 2 2 2 2
MC9S08QE128 MCU Series Reference Manual, Rev. 2
4 3
RTIE
0 0
Description
OSCOUT
Table 13-3. Changing the prescaler value clears the prescaler and
RTCPS
6 7 8 9
9 10
2 2 1 2
15 16 3 3
2 10 2x10 5x10
2 1
RTCPS
0 0
Power On Reset (POR) Default
10 11 12 13
2 4 2
2 10 2 10
3 4 4 4
10 2x10 5x10
Freescale Semiconductor
0
0
14 15
2 3
5x10 10
5 5
10 2x10