HD404374 Datasheet, PDF (67/161 Pages) Renesas Technology Corp – Low-Voltage AS Microcomputers with On-Chip A/D Converter

HD404374/HD404384/HD404389/HD404082/HD404084 Series
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
Prescaler W
System clock in active and MCU reset, stop mode
standby modes, subsystem clearance
clock in subactive mode*¹
Clock obtained by division-
by-8 of 32.768 kHz
oscillation by subsystem
clock oscillator
MCU reset, software*²
MCU reset, stop mode,
watch mode*¹
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.
Rev.5.00, Sep.11.2003, page 67 of 161