Datasheet

Section 17 Subsystem Timer (Subtimer)
Rev. 4.00 Mar. 15, 2006 Page 379 of 556
REJ09B0026-0400
Section 17 Subsystem Timer (Subtimer)
The subtimer is a timer for controlling subsystem which has an on-chip oscillator for supplying
system clocks in subactive and subsleep modes and an on-chip 8-bit down counter. Since the
subtimer has a prescaler that can set the division ratio by software, it can supply a clock with any
frequency. This LSI has an on-chip single-channel subtimer.
17.1 Features
• On-chip oscillator
Oscillation frequency: 64 kHz to 850 kHz
Temperature characteristic: Source clock ± 10% (typ.)
• Counter: two
8-bit readable/writable down counter
8-bit counter for measuring oscillation frequency of the on-chip oscillator
• CPU interrupt source
Underflow (interrupt interval: 731 µsec to 67.4 msec)
• Subtimer clock supply operating modes:
Subactive mode
Subsleep mode
• On-chip oscillator
The on-chip oscillator supplies three kinds of clocks:
Subactive or subsleep mode (φ
w
)
Subtimer down counter (input clock)
Watchdog timer (input clock)
• Subtimer prescaler (SBTPS)
The subtimer prescaler is a divider which controls input clocks to the counter which measures
oscillation cycle of the on-chip oscillator and the down counter for the subtimer.