mc9s08dn60 Freescale Semiconductor, Inc, mc9s08dn60 Datasheet - Page 255

• Manufacturer Part Number: mc9s08dn60
• Description: Hcs08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

14.4
The RTC is composed of a main 8-bit up-counter with an 8-bit modulo register, a clock source selector,
and a prescaler block with binary-based and decimal-based selectable values. The module also contains
software selectable interrupt logic.
After any MCU reset, the counter is stopped and reset to 0x00, the modulus register is set to 0x00, and the
prescaler is off. The 1-kHz internal oscillator clock is selected as the default clock source. To start the
prescaler, write any value other than zero to the prescaler select bits (RTCPS).
Three clock sources are software selectable: the low power oscillator clock (LPO), the external clock
(ERCLK) and the internal clock (IRCLK). The RTC clock select bits (RTCLKS) are used to select the
desired clock source. If a different value is written to RTCLKS, the prescaler and RTCCNT counters are
reset to 0x00.
RTCPS and the RTCLKS[0] bit select the desired divide-by value. If a different value is written to RTCPS,
the prescaler and RTCCNT counters are reset to 0x00.
Freescale Semiconductor
RTCPS
Functional Description
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
source prescaler period
1-kHz internal clock
(RTCLKS = 00)
128 ms
256 ms
512 ms
1.024 s
32 ms
64 ms
10 ms
16 ms
8 ms
1 ms
2 ms
4 ms
0.1 s
0.5 s
Off
1 s
MC9S08DN60 Series Data Sheet, Rev 2
source prescaler period
Table 14-6. Prescaler Period
1-MHz external clock
(RTCLKS = 01)
1.024 ms
2.048 ms
4.096 ms
8.192 ms
16.4 ms
32.8 ms
65.5 ms
10 ms
20 ms
50 ms
1 ms
2 ms
5 ms
0.1 s
0.2 s
Off
Table 14-6
source prescaler period
32-kHz internal clock
(RTCLKS = 10)
15.625 ms
3.125 ms
31.25 ms
31.25 µs
312.5 µs
62.5 µs
250 µs
125 µs
0.5 ms
16 ms
32 ms
1 ms
2 ms
4 ms
8 ms
shows different prescaler period values.
Off
Chapter 14 Real-Time Counter (S08RTCV1)
source prescaler period
32-kHz internal clock
(RTCLKS = 11)
156.25 ms
31.25 ms
312.5 ms
1.5625 s
62.5 ms
128 ms
256 ms
512 ms
1.024 s
2.048 s
0.625 s
3.125 s
32 ms
64 ms
6.25 s
Off
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