LAPIS Semiconductor ML610421, User Manual, Page: 100 / 437

ML610Q421/ML610Q422/ML610421 User’s Manual
Chapter 6 Clock Generation Circuit
6 – 7
6.3.1.2 Operation of Low-Speed Clock Generation Circuit
The low-speed clock generation circuit is activated by the occurrence of power ON reset.
A low-speed clock (LSCLK) is supplied to the peripheral circuits after the elapse of the low-speed oscillation start
period (T
XTL
) and oscillation stabilization period (8192 counts) after powered on.
The low-speed clock generation circuit stops the oscillation in STOP mode. When oscillation is resumed by releasing of
the STOP mode by external interrupt, LSCLK is supplied to the peripheral circuits after the elapse of the low-speed
oscillation start period (T
XTL
) and low-speed clock (LSCLK) oscillation stabilization period. For STOP mode, see
Chapter 4, “MCU Control Function”.
Figure 6-3 shows the waveforms of the low-speed clock generation circuit. For the low-speed oscillation start time
(T
XTL
), see Appendix C, “Electrical Characteristics”.
Figure 6-3 Operation of Low-Speed Clock Generation Circuit
Note:
After the power supply is turned on, CPU starts operation with a high-speed clock (500 kHz RC oscillation). It is
recommended to switch to the low-speed clock after confirming that the low-speed clock is oscillating by checking that
the 128 Hz interrupt request bit (Q128H) of the low-speed time base counter is “1”. If the clock is switched before the
low-speed clock oscillates, the CPU stops operation until oscillation of the low-speed clock starts.
Low-speed clock
oscillation waveform
Reset of voltage regulator
for low-speed oscillation
RESET_VRX
T
XTL
: Oscillation start time T
XTL
: Oscillation start time
Power supply V
DD
RESET
Start of LSCLK
supply
Occurrence of
external interrupt
Start of LSCLK
supply
Low-speed oscillation
Count: 8192
Low-speed clock
LSCLK
Low-speed oscillation
Count: 4096
Low-speed oscillation
Count: 4096
LSCLK waveform
Low-speed oscillation
Count: 8192
LSCLK waveform
Low-speed clock oscillation waveform Low-speed clock oscillation waveform
STOP
mode