68HC705JB2 datasheet(43/128 Pages) NXP

43 / 128 page

August 28, 1998

GENERAL RELEASE SPECIFICATION

LOW POWER MODES

REV 1.1

6-1

SECTION 6

LOW POWER MODES

The MC68HC705JB2 has two low-power operating modes: STOP mode and

WAIT mode.

The STOP and WAIT instructions provide two modes that reduce the power

required for the MCU by stopping various internal clocks and/or the oscillator. The

ﬂow of the STOP, and WAIT modes are shown in Figure 6-1.

6.1

STOP MODE

Execution of the STOP instruction in this mode places the MCU in its lowest

power consumption mode. In the STOP Mode the internal oscillator is turned off,

halting all internal processing.

Execution of the STOP instruction automatically clears the I-bit in the Condition

Code Register and sets the IRQE enable bit in the IRQ Control/Status Register so

that the IRQ external interrupt is enabled. All other registers, including the other

bits in the TCSR, and memory remain unaltered. All input/output lines remain

unchanged.

The MCU can be brought out of the STOP Mode by an IRQ external interrupt or a

USB coming out from Suspend Mode Interrupt (Bus activity detection) or an

externally generated RESET, USB Reset or an LVR reset. When exiting the STOP

Mode the internal oscillator will resume after a 128 or 4064 internal processor

clock cycle oscillator stabilization delay.

6.2

WAIT MODE

The WAIT instruction places the MCU in a low-power mode, which consumes

more power than the STOP Mode. In the WAIT Mode the internal processor clock

is halted, suspending all processor and internal bus activity. Execution of the

WAIT instruction automatically clears the I-bit in the Condition Code Register and

sets the IRQE enable bit in the IRQ Control/Status Register so that the IRQ

external interrupt is enabled. All other registers, memory, and input/output lines

remain in their previous states.

The WAIT Mode may be exited when an external IRQ or a USB or Timer1 or MFT

interrupt, an LVR reset or an external RESET occurs.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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