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Low Power Modes; Overview Of Operating Mode Transitions - Hitachi H8/300L Series Manual

Single-chip microcomputer
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Low Power Modes

The H8/300L Series microcomputers support active (high speed) mode in which programs are
executed rapidly, and seven low power modes in which the IC power dissipation is
significantly reduced. There are two low power modes in which programs are executed at
relatively low speeds, namely, active (medium speed) mode and subactive mode. The five
modes in which CPU operation is stopped are sleep (high speed) mode, sleep (medium speed)
mode, sub-sleep mode, watch mode, and standby mode. Please refer to section 3, "Product
Series and Operating Modes" for operating mode details for individual products, since the low
power modes differ between products in the H8/300L Series.

1. Overview of Operating Mode Transitions

Active (High Speed) Mode
In active (high speed) mode the CPU operates at high speed based on a system clock with a
5 MHz operating frequency when the oscillator frequency is 10 MHz.
Active (Medium Speed) Mode
In active (medium speed) mode the CPU operates at a relatively lower speed based on a
system clock generated by dividing a 5 MHz clock operating frequency (when the oscillator
frequency is 10 MHz). The clock division ratio differs depending on the individual product.
Subactive Mode
In subactive mode the system clock oscillator used in active mode is stopped and the CPU
operates at low speed and low power based on a subclock (16384 Hz, 8192 Hz, or 4096 Hz)
generated by dividing a 32.768 kHz oscillator frequency.
Sleep (High Speed) Mode
In sleep (high speed) mode the on-chip peripheral modules operate based on a 5 MHz system
clock (when the oscillator frequency is 10 MHz).
Sleep (Medium Speed) Mode
In sleep (medium speed) mode the on-chip peripheral modules operate based on a system clock
generated by dividing a 5 MHz clock (when the oscillator frequency is 10 MHz). The clock
division ratio differs depending on the individual product.
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