SH7041A datasheet(112/923 Pages) RENESAS

112 / 923 page

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.

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

that has requested them.

2.5.2

Power-Down State

Besides the ordinary program execution states, the CPU also has a power-down state in which

CPU operation halts, lowering power consumption. There are two power-down state modes: sleep

mode and standby mode.

Sleep Mode: When 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 cache

(or on-chip RAM) is maintained. The on-chip peripheral modules other than the CPU do not halt

in the sleep mode.

To return from sleep mode, use a reset (power-on or manual), any interrupt, or a DMA address

error; the CPU returns to the ordinary program execution state through the exception processing

state.

Standby Mode: To enter the standby mode, set the standby bit SBY (in the standby control

peripheral module, and oscillator functions are halted. However, when entering standby mode, the

DMA master enable bit of the DMAC should be set to 0. If multiplication-related instructions are

being executed at the time of entry into standby mode, the values of MACH and MACL will

become undefined.

To return from standby mode, use a reset (power-on or manual) or an NMI interrupt. For resets,

the CPU returns to ordinary program execution state through the exception processing state when

placed in a reset state for the duration of the oscillator stabilization time. For NMI interrupts, the

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