HD404639R Datasheet, PDF (59/135 Pages) Renesas Technology Corp – 4-Bit Single-Chip Microcomputer

HD404639R Series
Prescalers
The MCU has the following two prescalers, S and W.
The prescalers operating conditions are listed in table 23, and the prescalers output supply is shown in
figure 39. The timers A–D input clocks except external events and the serial transmit clock except the
external clock are selected from the prescaler outputs, depending on corresponding mode registers.
Prescaler Operation
Prescaler S: 11-bit counter that inputs a 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 stop 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 23 Prescaler Operating Conditions
Prescaler
Prescaler S
Input Clock
System clock (in active and standby mode),
Subsystem clock (in subactive mode)
Reset Conditions
MCU reset
Prescaler W 32-kHz crystal oscillation
MCU reset, software
Stop Conditions
MCU reset,
stop mode,
watch mode
MCU reset,
stop mode
Subsystem
f_X/8
clock
f_X/4 or f_X/8
System
clock
Clock
selector
Prescaler W
Prescaler S
Figure 39 Prescaler Output Supply
Timer A
Timer B
Timer C
Timer D
Serial
interface 1
Serial
interface 2
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