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5.1
Overview
The H8/3857 Group and H8/3854 Group have seven modes of operation after a reset. These
include six power-down modes, in which power dissipation is significantly reduced.
Table 5.1 gives a summary of the seven operation modes.
Table 5.1
Operation Modes
Operating Mode
Active (high-speed) mode
Active (medium-speed) mode
Subactive mode
Sleep mode
Subsleep mode
Watch mode
Standby mode
Note:
*
This is a function of the H8/3857 Group only, and is not provided in the H8/3854 Group.
All the above operating modes except active (high-speed) mode are referred to as power-down
modes.
In this section the two active modes (high-speed and medium-speed) are referred to collectively as
active mode.
Figure 5.1 shows the transitions among these operation modes. Table 5.2 indicates the internal
states in each mode.
Section 5 Power-Down Modes
Description
The CPU runs on the system clock, executing program
instructions at high speed
The CPU runs on the system clock, executing program
instructions at reduced speed
The CPU runs on the subclock, executing program instructions
at reduced speed
The CPU halts. On-chip peripheral modules continue to operate
on the system clock.
The CPU halts. Timer A, timer C*, and the LCD controller
continue to operate on the subclock.
The CPU halts. The time-base function of timer A and the LCD
controller continue to operate on the subclock.
The CPU and all on-chip peripheral modules stop operating
5. Power-Down Modes
Rev.3.00 Jul. 19, 2007 page 101 of 532
REJ09B0397-0300
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