XC161 Datasheet, PDF (79/419 Pages) Infineon Technologies AG – 16-Bit Single-Chip Microcontroller with C166SV2 Core Volume 2 (of 2): Peripheral Units

XC161 Derivatives
Peripheral Units (Vol. 2 of 2)
Real Time Clock
15.3.1 48-bit Timer Operation
The concatenation of timers T14 and COUNT0 … COUNT3 can be regarded as a 48-bit
timer which is clocked with the RTC input frequency, optionally divided by the prescaler.
The reload registers T14REL, RELL, and RELH must be cleared to produce a true binary
48-bit timer. However, any other reload value may be used. Reload values other than
zero must be used carefully, due to the individual sections of the RTC timer with their
own individual overflows and reload values.
The maximum usable timespan is 2⁴⁸ (≈ 10¹⁴) T14 input clocks (assuming no prescaler),
which would equal more than 200 years at an oscillator frequency of 32 kHz.
15.3.2 System Clock Operation
A real time system clock can be maintained that keeps on running also during power
saving modes (optionally) and indicates the current time and date. This is possible
because the RTC module is not affected by a system reset¹⁾.
The resolution for this clock information is determined by the input clock of timer T14. By
selecting appropriate reload values each cascaded timer can represent directly a part of
the current time and/or date. Due to its width, T14 can adjust the RTC to the intended
range of operation (time or date). The maximum usable timespan is achieved when
T14REL is loaded with 0000_H and so T14 divides by 2¹⁶.
System Clock Example
The RTC count clock is f_OSCa (8:1 prescaler off). By selecting appropriate reload values
the RTC timers directly indicate the current time (see Figure 15-4 and Table 15-3).
3E8_H
REL3
04_H
REL2
04_H
REL1
018_H
REL0
FFDF_H
T14REL
CNT3
Hours
CNT2
Minutes
CNT1
Seconds
CNT0
1/1000
Seconds
T14
Prescaler
f_CNT =
32.768 kHz
MCA05414
Figure 15-4 RTC Configuration Example
Note: This setup can generate an interrupt request every millisecond, every second,
every minute, every hour, or every day.
1) After a power on reset, however, the RTC registers are undefined.
User’s Manual
RTC_X8, V2.1
15-10
V2.2, 2004-01