mc68hc05bs8 Freescale Semiconductor, Inc, mc68hc05bs8 Datasheet - Page 103

• Manufacturer Part Number: mc68hc05bs8
• Description: Mc68hc05 Family Of Low-cost Single-chip Microcontrollers.
• Manufacturer: Freescale Semiconductor, Inc

The MC68HC05BS8 has two low-power operating modes: the STOP mode and WAIT mode.
These two modes help to reduce the power required for the MCU by stopping various internal
clocks and/or the on-chip oscillator. The flow of the STOP and WAIT modes is shown in
Figure 11-1.
11.1
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.
When the CPU enters STOP mode, the I-bit in the Condition Code Register will be cleared
automatically. This enables the external hardware interrupt to “wake-up” the MCU. All other
registers and memory remain unchanged. All input/output lines remain unchanged.
The MCU can be brought out of the STOP mode only by a hardware interrupt or an externally
generated reset (POR or RESET). When exiting the STOP mode the internal oscillator will resume
after a 4064 internal processor clock cycle oscillator stabilization delay.
Note:
11.2
The WAIT instruction places the MCU in a low power 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 sub-systems, or a reset 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.
MC68HC05BS8
The STOP mode cannot be entered if the COP watchdog timer is running.
STOP Mode
WAIT Mode
LOW POWER MODES
LOW POWER MODES
11
TPG
11