Section 5 Power-Down Modes
5.1
Overview
The H8/3887 Series has nine modes of operation after a reset. These include eight power-down
modes, in which power dissipation is significantly reduced. Table 5-1 gives a summary of the
eight operating modes.
Table 5-1 Operating Modes
Operating Mode
Description
Active (high-speed) mode
The CPU and all on-chip peripheral functions are operable on the
system clock in high-speed operation
Active (medium-speed) mode The CPU and all on-chip peripheral functions are operable on the
system clock in low-speed operation
Subactive mode
The CPU is operable on the subclock in low-speed operation
Sleep (high-speed) mode
The CPU halts. On-chip peripheral functions are operable on the
system clock
Sleep (medium-speed) mode The CPU halts. On-chip peripheral functions operate at a
frequency of 1/64, 1/32, 1/16, or 1/8 of the system clock frequency
Subsleep mode
The CPU halts. The time-base function of timer A, timer C, timer
G, timer F, WDT, SCI1, SCI3-1, SCI3-2, AEC and LCD
controller/driver are operable on the subclock.
Watch mode
The CPU halts. The time-base function of timer A, timer F, timer
G, AEC and LCD controller/driver are operable on the subclock.
Standby mode
The CPU and all on-chip peripheral functions halt
Module standby mode
Individual on-chip peripheral functions specified by software enter
standby mode and halt
Of these nine operating modes, all but the active (high-speed) mode are power-down modes. In
this section the two active modes (high-speed and medium speed) will be 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.
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ETC [ ETC ]
