HD404372 datasheet(67/161 Pages) RENESAS

67 / 161 page

HD404374/HD404384/HD404389/HD404082/HD404084 Series

Rev.5.00, Sep.11.2003, page 67 of 161

Prescalers

The MCU has the following prescalers, S and W (HD404374 Series).

The operating conditions for each prescaler are shown in table 24, and the output supply destinations in

figure 31.

Timer A to C input clocks other than external events, and serial transfer clocks other than external clocks

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

*1. It does not stop in any other modes.

Prescaler W (PSW) (HD404374 Series):

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

standby modes, subsystem

clock in subactive mode*

MCU reset, stop mode

clearance

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

Notes: *1 Applies to HD404374 Series

*2 If bits TMA3 to TMA1 in timer mode register A (TMA) are all set to 1, PSW is cleared to $00.

HD404372 Datasheet(PDF) 67 Page - Renesas Technology Corp