SH7708 datasheet(66/633 Pages) RENESAS

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2.5

Processor States and Processor Modes

2.5.1

Processor States

The SH7708 Series has five processor states: the reset state, exception-handling state, bus-released

state, program execution state, and power-down state.

Reset State: In this state the CPU is reset. The reset state is entered when the

RESET pin goes

low. The CPU enters the power-on reset state if the

BREQ pin is high, or the manual reset state if

the

BREQ pin is low. See section 4, Exception Handling, for more information on resets.

In the power-on reset state, the internal states of the CPU and the on-chip supporting module

registers are initialized. In the manual reset state, the internal states of the CPU and registers of on-

chip supporting modules other than the bus state controller (BSC) are initialized. Since the BSC is

not initialized in the manual reset state, refreshing operations continue. Refer to the register

configurations in the relevant sections for further details.

Exception-Handling State: This is a transient state during which the CPU’s processor state flow

is altered by a reset, general exception, or interrupt exception handling.

In the case of a reset, the CPU branches to address H'A0000000 and starts executing the user-

coded exception handling program.

In the case of a general exception or interrupt, the program counter (PC) contents are saved in the

saved program counter (SPC) and the status register (SR) contents are saved in the saved status

found from the sum of the contents of the vector base address and the vector offset. See section 4,

Exception Processing, for more information on resets, general exceptions, and interrupts.

Program Execution State: In this state the CPU executes program instructions in sequence.

Power-Down State: In the power-down state, CPU operation halts and power consumption is

reduced. The power-down state is entered by means of the SLEEP instruction or the CA pin*.

There are three modes in the power-down state: sleep mode, standby mode and hardware standby

mode. See section 8, Power-Down Modes, for more information.

Note:SH7708S,SH7708R only

Bus-Released State: In this state the CPU has released the bus to a device that requested it.

Transitions between the states are shown in figure 2.8.

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