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Program execution state
Exception-handling state
End of exception
handling
Sleep mode
Reset state
SLEEP instruction
Power-down state
RES
= 0
RES
= 0
RES
= 1
I/O-1/
IRQ
= 0 or
I/O-2/
IRQ
Figure 2.12 State Transitions
2.6.2
Program Execution State
In this state the CPU executes program instructions in normal sequence.
2.6.3
Exception-Handling State
This is a transitory state entered in response to a reset or interrupt. In interrupt exception handling,
the stack pointer is referenced and the program counter and condition code register are saved.
2.6.4
Power-Down State
The power-down state consists of a sleep mode.
Sleep mode is entered from the program execution state when the SLEEP instruction is executed.
Operation of the CPU, clocks, and all other on-chip peripheral modules is halted. The on-chip
peripheral modules enter the reset state, but the contents of CPU registers and on-chip RAM are
retained as long as the specified voltage is supplied. The I/O port DR and DDR values are also
retained.
Sleep mode is cleared by a low input to the
RES
, I/O-1/
IRQ
, or I/O-2/
IRQ
pin.