Section 22 Power-Down Modes; Overview - Hitachi H8S/2646 Hardware Manual

Section 22 Power-Down Modes

22.1

Overview

In addition to the normal program execution state, the H8S/2646 Series has nine power-down
modes in which operation of the CPU and oscillator is halted and power dissipation is reduced.
Low-power operation can be achieved by individually controlling the CPU, on-chip supporting
modules, and so on.
The H8S/2646 Series operating modes are as follows:
(1) High-speed mode
(2) Medium-speed mode
(3) Subactive mode
(4) Sleep mode
(5) Subsleep mode
(6) Watch mode
(7) Module stop mode
(8) Software standby mode
(9) Hardware standby mode
(2) to (9) are low power dissipation states. Sleep mode and sub-sleep mode are CPU states,
medium-speed mode is a CPU and bus master state, sub-active mode is a CPU and bus master and
internal peripheral function state, and module stop mode is an internal peripheral function
(including bus masters other than the CPU) state. Some of these states can be combined.
After a reset, the LSI is in high-speed mode with modules other than the DTC in module stop
mode.
Table 22-1 shows the internal state of the LSI in the respective modes. Table 22-2 shows the
conditions for shifting between the low power dissipation modes.
Figure 22-1 is a mode transition diagram.
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