Cpu States; Overview - Hitachi H8/3664 Hardware Manual

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2.8

CPU States

2.8.1

Overview

There are four CPU states: the reset state, program execution state, program halt state, and
exception-handling state. The program execution state includes active mode and subactive mode.
In the program halt state there are a sleep mode, standby mode, and sub-sleep mode. These states
are shown in figure 2.13. Figure 2.14 shows the state transitions. For details on program execution
state and program halt state, refer to section 6, Power-Down Modes. For details on exception
processing, refer to section 3, Exception Handling.
CPU state
A state in which some
or all of the chip
functions are stopped
to conserve power
A transient state in which the CPU changes
the processing flow due to a reset or an interrupt
Note: See section 6, Power-Down Modes, for details on the modes and their transitions.
Reset state
The CPU is initialized
Program
execution state
Program halt state
Exception-
handling state
Figure 2.13 CPU Operation States
Active
(high speed) mode
The CPU executes successive program
instructions at high speed,
synchronized by the system clock
Subactive mode
The CPU executes
successive program
instructions at reduced
speed, synchronized
by the subclock
Sleep mode
Standby mode
Subsleep mode
Power-down
modes
41

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