HITACHI 433
Section 18 Power-Down States
18.1
Overview
In the power-down mode, all CPU functions are halted. This lowers power consumption
dramatically.
18.1.1
Power-Down Modes
The SH microprocessor has two power-down modes.
1. Sleep mode
2. Standby mode
The sleep mode and standby mode are entered from the program execution state according to the
transition conditions given in table 18.1. Table 18.1 also describes procedures for canceling each
mode and the states of the CPU and peripheral functions.
Table 18.1
Power-Down States
State
Mode
Sleep
mode
Entering
Procedure
Execute
SLEEP
instruction
with SBY
bit set to 0
in SBYCR
Clock
Run
CPU
Halt
Peripheral
Functions
Run
CPU
Registers RAM
Held
I/O
Ports
Held
Canceling
Procedure
Interrupt
DMA
address
error
Power-on
reset
Manual
reset
NMI
Power-on
reset
Manual
reset
Held
Standb
y mode
Execute
SLEEP
instruction
with SBY
bit set to 1
in SBYCR
Halt
Halt
Halt*
1
Held
Held
Held or
high-Z*
2
SBYCR: Standby control register
SBY: Standby bit
Notes: 1. Some of the registers of the on-chip peripheral modules are not initialized in the
standby mode. For details, see table 18.3, Status of Registers in the Standby Mode in
section 18.4.1, Transition to the Standby Mode, or the descriptions of registers given
where the on-chip peripheral modules are covered.
2. The status of I/O ports in the standby mode are set by the port high-impedance bit (HIZ)
of the SBYCR. See section 18.2, Standby Control Register (SBYCR) for details. The
status of pins other than the I/O ports are described in appendix B, Pin States.