68HC05CL48 datasheet(45/145 Pages) MOTOROLA

45 / 145 page

June 11, 1997

GENERAL RELEASE SPECIFICATION

MC68HC05CL48

LOW POWER MODES

MOTOROLA

REV 2.0

6-1

SECTION 6

LOW POWER MODES

6.1

LOW-POWER MODES

The MC68HC05CL48 has two low-power operational modes. The WAIT and

STOP instructions provide two 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.

The ﬂow of the STOP and WAIT modes is shown in Figure 6-1.

6.1.1 STOP Instruction

Execution of the STOP instruction, places the MCU in its lowest power

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

all internal processing, including the COP Watchdog Timer.

When the CPU enters STOP Mode, the I-bit in the Condition Code Register will be

cleared automatically. This enable the external hardware interrupt to wake up the

MCU. 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 a Caller ID (RT_L)

interrupt, WTIMER interrupt, a hardware interrupt “IRQ, IRQ(n), KBI(n)” or an

externally generated RESET. When exiting the STOP Mode the internal oscillator

will resume after a 488 internal processor clock cycle oscillator stabilization delay.

6.1.2 WAIT Instruction

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. Other Internal clocks

remain active, permitting interrupts to be generated from the functional blocks, or

a reset to be generated from the COP Watchdog Timer. The Timer may be used to

generate a periodic exit from the WAIT Mode. Execution of the WAIT instruction

automatically clears the I-bit in the Condition Code Register, so that any hardware

interrupt can wake up the MCU. All other registers, memory, and input/output lines

remain in their previous states.

68HC05CL48 Datasheet(PDF) 45 Page - Motorola, Inc