SH7021 datasheet(64/509 Pages) RENESAS

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On a power-on reset, all CPU internal states and on-chip peripheral module registers are

initialized. In a manual reset, all CPU internal states and on-chip peripheral module registers, with

the exception of the bus state controller (BSC) and pin function controller (PFC), are initialized.

On a manual reset, the BSC is not initialized, so the refresh operation will continue.

Exception Processing State: Exception processing is a transient state that occurs when the CPU’s

processing state flow is altered by exception processing sources such as resets or interrupts.

For a reset, the initial values of the program counter PC (execution start address) and stack pointer

SP are fetched from the exception processing vector table and stored; the CPU then branches to

the execution start address and execution of the program begins.

For an interrupt, the stack pointer (SP) is accessed and the program counter (PC) and status

from the exception processing vector table; the CPU then branches to that address and the program

starts executing, thereby entering the program execution state.

Program Execution State: In the program execution state, the CPU sequentially executes the

program.

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

declines. The SLEEP instruction places the CPU in the power-down state. This state has two

modes: sleep mode and standby mode. This is described in more detail in section 2.5.1, Power-

Down State.

Bus Release State: In the bus release state, the CPU releases rights to the bus to the device that

has requested them.

2.5.2

Power-Down State

In addition to the ordinary program execution states, the CPU also has a power-down state in

which CPU operation halts and power consumption is lowered. There are two power-down state

modes: sleep mode and standby mode.

Sleep Mode: When the standby bit SBY (in the standby control register SBYCR) is cleared to 0

and a SLEEP instruction executed, the CPU moves from program execution state to sleep mode.

In the sleep mode, the CPU halts and the contents of its internal registers and the data in on-chip

RAM are stored. The on-chip peripheral modules other than the CPU do not halt in the sleep

mode.

To return from sleep mode, use a reset, any interrupt, or a DMA address error; the CPU returns to

ordinary program execution state through the exception processing state.

SH7021 Datasheet(PDF) 64 Page - Renesas Technology Corp