MC9S08JM16CGTE FREESCALE [Freescale Semiconductor, Inc], MC9S08JM16CGTE Datasheet - Page 214

• Manufacturer Part Number: MC9S08JM16CGTE
• Description: Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Real-Time Counter (S08RTCV1)
13.3.2
RTC
13.3.3
13.4
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) select the desired clock
source. If a different value is written to RTCLKS, the prescaler and RTCCNT counters are reset to 0x00.
214
RTCMOD
RTCCNT
Field
Field
CNT is the read-only value of the current RTC count of the 8-bit counter.
7:0
7:0
Reset:
Reset:
Functional Description
W
W
R
R
RTC Count. These eight read-only bits contain the current value of the 8-bit counter. Writes have no effect to this
register. Reset, writing to RTCMOD, or writing different values to RTCLKS and RTCPS clear the count to 0x00.
RTC Modulo. These eight read/write bits contain the modulo value used to reset the count to 0x00 upon a compare
match and set the RTIF status bit. A value of 0x00 sets the RTIF bit on each rising edge of the prescaler output.
Writing to RTCMOD resets the prescaler and the RTCCNT counters to 0x00. Reset sets the modulo to 0x00.
RTC
RTC
Counter Register (
Modulo Register (
7
0
7
0
0
0
6
Figure 13-4. RTC Counter Register (RTCCNT)
6
Figure 13-5. RTC Modulo Register (RTCMOD)
Table 13-5. RTCMOD Field Descriptions
Table 13-4. RTCCNT Field Descriptions
MC9S08JM16 Series Data Sheet, Rev. 2
0
0
5
5
RTC
RTC
MOD)
CNT)
0
0
4
4
Description
Description
RTCMOD
RTCCNT
0
0
3
3
0
0
2
2
Freescale Semiconductor
0
0
1
1
0
0
0
0