HD404629R Datasheet, PDF (60/157 Pages) Renesas Technology Corp – AS Microcomputer Incorporating a DTMF Generator Circuit

HD404629R Series
Prescalers
The MCU has the following two prescalers, S and W.
The prescalers operating conditions are listed in table 25, and the prescalers output supply is shown in
figure 42. The timers A–D input clocks except external events, the serial transmit clock except the external
clock, and the LCD circuit operating clock are selected from the prescaler outputs, depending on
corresponding mode registers.
Prescaler Operation
Prescaler S: 11-bit counter that inputs the system clock signal. After being reset to $000 by MCU reset,
prescaler S divides the system clock. Prescaler S keeps counting, except in watch and subactive modes and
at MCU reset.
Prescaler W: Five-bit counter that inputs the X1 input clock signal (32-kHz crystal oscillation) divided by
eight. After being reset to $00 by MCU reset, prescaler W divides the input clock. Prescaler W can be
reset by software.
Table 25 Prescaler Operating Conditions
Prescaler
Prescaler S
Prescaler W
Input Clock
System clock (in active and standby mode),
Subsystem clock (in subactive mode)
Reset Conditions
MCU reset
32-kHz crystal oscillation
MCU reset,
software
Stop Conditions
MCU reset,
stop mode,
watch mode
MCU reset,
stop mode
Subsystem
clock
Prescaler W
System
clock
Clock
selector
Prescaler S
Figure 42 Prescaler Output Supply
LCD
Timer A
Timer B
Timer C
Timer D
Serial
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