Fujitsu FR81S User Manual
CHAPTER 29: RTC/WDT1 CALIBRATION
2. Features
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER : RTC/WDT1 CALIBRATION
FUJITSU SEMICONDUCTOR CONFIDENTIAL
4
2. Features
This section explains features of the RTC/WDT1 calibration.
RTC Clock source select register
The main clock or the sub clock can be selected. For information on how to select, see "CHAPTER:
CLOCK".
Real-Time Clock (RTC) Calibration (This function is effective only when the sub clock is used.)
Values of the sub second register of the RTC are determined by calculating the sub clock frequency
from the main clock frequency on the condition that both the main clock driven counter and the sub
clock driven counter operate concurrently (Figure 2-1).
WDT1(CR clock) calibration
This device has no CR clock calibration function. CR clock errors, however, can be measured by
using the register of this module.
Figure 2-1 Comparison of Counters Driven by Different Clocks
Sub clock/
CR oscillation clock
Sub/CR counter
Main oscillation
counter
CUTD
CUTD-1
New CUTR
Old CUTR
2
1
0
Comparison in progress
MB91520 Series
MN705-00010-1v0-E
1073