HC805P18GRSSLASHD datasheet(41/111 Pages) NXP

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GENERAL RELEASE SPECIFICATION

OPERATING MODES

Rev. 1.0

6.3 Low-Power Modes

The MC68HC805P18 is capable of running in a low-power mode in each of its

configurations. The WAIT and STOP instructions provide modes that reduce the

power required for the MCU by stopping various internal clocks and/or the on-chip

oscillator. The STOP and WAIT instructions are not normally used if the COP

watchdog timer is enabled (MOR1, bit 0). The stop conversion to halt option

(MOR1, bit 5) is used to modify the behavior of the STOP instruction from stop

mode to halt mode. The flow of the stop, halt, and wait modes is shown in

Figure 6-2.

6.4 STOP Instruction

The STOP instruction can result in one of two modes of operation depending on

the option programmed in the mask option register 1. If the stop conversion to halt

option (MOR1,bit 5) is not chosen, the STOP instruction will behave like a normal

STOP instruction in the M68HC805 Family and place the MCU in the stop mode.

If the stop conversion to halt option is chosen, the STOP instruction will behave like

a WAIT instruction (with the exception of a brief delay at startup) and place the

MCU in the halt mode.

6.4.1 Stop Mode

Execution of the STOP instruction (without conversion to halt) places the MCU in

its lowest-power consumption mode. In the stop mode, the internal oscillator is

turned off stopping all internal processing including the COP watchdog timer. The

RC oscillator that feeds the EEPROM and the A/D converter is also stopped.

Execution of the STOP instruction automatically clears the I bit in the condition

code register so that the IRQ external interrupt is enabled. All other registers and

memory remain unaltered. All input/output lines remain unchanged.

The MCU can be brought out of the stop mode only by an IRQ external interrupt

(or port A, if selected as an option in the MOR2) or an externally generated reset.

When exiting the stop mode, the internal oscillator will resume after a 4064 PH2

clock cycle oscillator stabilization delay.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

HC805P18GRS/D Datasheet(PDF) 41 Page - NXP Semiconductors