E202075_HD404889 Datasheet, PDF (81/202 Pages) Renesas Technology Corp – Low-Voltage AS Microcomputers with On-Chip LCD Circuit

HD404889/HD404899/HD404878/HD404868 Series
Prescalers
The MCU has the following two prescalers, S and W.
The operating conditions for each prescaler are shown in table 24, and the output supply destinations in
figure 34.
Timer A to D input clocks other than external events, serial transfer clocks other than external clocks, and
the LCD circuit operating clock are selected from the prescaler outputs in accordance with the respective
mode register.
Prescaler Operation
Prescaler S (PSS):
Prescaler S is an 11-bit counter that has the system clock as input. When the MCU is reset, prescaler S is
reset to $000, then divides the system clock. Prescaler S operation is stopped by a reset by the MCU, and
in stop mode and watch mode. It does not stop in any other modes.
Prescaler W (PSW):
Prescaler W is a counter that has a clock divided from the X1 input (32 kHz crystal oscillation) as input.
When the MCU is reset, prescaler W is reset to $00, then divides the input clock. Prescaler W can also be
reset by software.
Table 24 Prescaler Operating Conditions
Prescaler
Input Clock
Reset Conditions
Stop Conditions
Prescaler S
System clock in active and MCU reset, Stop mode
standby modes, Subsystem clearance
clock in subactive mode
MCU reset, Stop mode,
Watch mode
Prescaler W
Clock obtained by division-
by-8 of 32.768 kHz
oscillation by subsystem
clock oscillator
MCU reset, Software*
MCU reset, Stop mode
Note: If bits TMA3 to TMA1 in timer mode register A (TMA) are all set to 1, PSW is cleared to $00.
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