Freescale Semiconductor ColdFire MCF52210 - Manual (Page 173)

Functional Description
MCF52211 ColdFire® Integrated Microcontroller Reference Manual, Rev. 2
Freescale Semiconductor 11-13
Figure 11-13. RTC General Oscillator Count Lower Register (RTCGOCL)
11.3 Functional Description
The RTC uses a supplied 1 Hz signal to increment the seconds, minutes, hours, and days TOD counters.
The alarm functions, when enabled, generate RTC interrupts when the TOD settings reach programmed
values. The minute stopwatch allows for efficient interrupts on minute boundaries.
The 1 Hz clock and the sampling clock are affected by the value of RTCGOCNT (see Section 11.2.1.11,
“RTC General Oscillator Count Registers (RTCGOCU and RTCGOCL) ”) as follows:
• The 1 Hz clock is the input clock divided by RTCGOCNT[31:0].
• The sampling clock is the input clock divided by RTCGOCNT[31:9].
• If RTCGOCNT equals 0x0, the 1 Hz clock is shut down completely.
Table 11-14 presents several examples of this functionality.
11.3.1 Prescaler and Counter
A 1 Hz clock is supplied to the RTC. This 1 Hz clock drives the RTC’s counters. The counter portion of
the RTC module consists of four groups of counters that are physically located in three registers:
• The 6-bit seconds counter is located in the SECONDS register
• The 6-bit minutes counter and the 5-bit hours counter are located in the HOURMIN register
• The 16-bit day counter is located in the DAYR register
These counters cover a 24-hour clock over 65536 days. All three registers can be read or written at any
time.
IPSBAR
Offset: 0x03F8 (RTCGOCL)
Access: User read/write
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
R
RTCGOCNT[15:0]
W
Reset 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Table 11-13. RTCGOCL Field Descriptions
Field Description
15–0
RTCGOCNT[15:0]
RTC general oscillator count, bits 15:0. This field is used to control the 1 Hz clock and the sampling clock
as described in
Section 11.3, “Functional Description ”.
Table 11-14. Sample RTC parameter values
Sampling clock
frequency
RTCGOCNT[31:0]
value for 1 Hz
Divider output
frequency
RTCGOCNT[31:9]
value for 512 Hz
Output clock
frequency
32.000 kHz 0x7D00
1 Hz
0x3E 516.1 Hz
32.768 kHz 0x8000 0x40 512 Hz
38.400 kHz 0x9600 0x4B 512 Hz
48.000 kHz 0xBB80 0x5D 516.1 Hz