MC9S08DZ16 FREESCALE [Freescale Semiconductor, Inc], MC9S08DZ16 Datasheet - Page 315

• Manufacturer Part Number: MC9S08DZ16
• Description: 8-Bit HCS08 Central Processor Unit (CPU)
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

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.
The RTC modulo register (RTCMOD) allows the compare value to be set to any value from 0x00 to 0xFF.
When the counter is active, the counter increments at the selected rate until the count matches the modulo
value. When these values match, the counter resets to 0x00 and continues counting. The real-time interrupt
flag (RTIF) is set when a match occurs. The flag sets on the transition from the modulo value to 0x00.
Writing to RTCMOD resets the prescaler and the RTCCNT counters to 0x00.
The RTC allows for an interrupt to be generated when RTIF is set. To enable the real-time interrupt, set
the real-time interrupt enable bit (RTIE) in RTCSC. RTIF is cleared by writing a 1 to RTIF.
15.4.1
This section shows an example of the RTC operation as the counter reaches a matching value from the
modulo register.
Freescale Semiconductor
RTCPS
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
RTC Operation Example
1-kHz Internal Clock
(RTCLKS = 00)
256 ms
512 ms
1.024 s
128 ms
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
MC9S08DZ60 Series Data Sheet, Rev. 4
1-MHz External Clock
Table 15-6. Prescaler Period
(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 15-6
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 15 Real-Time Counter (S08RTCV1)
32-kHz Internal Clock
(RTCLKS = 11)
156.25 ms
31.25 ms
312.5 ms
1.5625 s
62.5 ms
0.625 s
3.125 s
128 ms
256 ms
512 ms
1.024 s
2.048 s
32 ms
64 ms
6.25 s
Off
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