HD404449 Datasheet, PDF (55/123 Pages) Hitachi Semiconductor – HD404449 SERIES

HD404449 Series
Prescalers
The MCU has the following two prescalers, S and W.
The prescaler operating conditions are listed in table 25, and the prescaler output supply is shown in figure
39. The timer 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 stop, 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
Reset Conditions
System clock (in active
and standby mode),
Subsystem clock (in
subactive mode)
MCU reset
32-kHz crystal oscillation Software
Stop Conditions
MCU reset, stop mode,
watch mode
MCU reset, stop mode
Subsystem ^fX^/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 1
Serial 2
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