MC68HC05B6_13 Datasheet, PDF (36/302 Pages) Freescale Semiconductor, Inc – Microcontrollers

2.4.2 WAIT
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The WAIT instruction places the MCU in a low power consumption mode, but WAIT mode
consumes more power than STOP mode. All CPU action is suspended and the watchdog is
disabled, but the timer, A/D and SCI systems remain active and operate as normal (see flowchart
in Figure 2-3). All other memory and registers remain unaltered and all parallel input/output lines
remain unchanged. The programming or erase mechanism of the EEPROM is also unaffected, as
well as the charge pump high voltage generator.
During WAIT mode the I-bit in the CCR is cleared to enable all interrupts. The INTE bit in the
miscellaneous register (Section 2.5) is not affected by WAIT mode. When any interrupt or reset is
sensed, the program counter vectors to the locations containing the start address of the interrupt
or reset service routine.
Any IRQ, timer (overflow, input capture or output compare) or SCI interrupt (in addition to a logic
low on the RESET pin) causes the processor to exit WAIT mode.
If a non-reset exit from WAIT mode is performed (i.e. timer overflow interrupt exit), the state of the
remaining systems will be unchanged.
If a reset exit from WAIT mode is performed the entire system reverts to the disabled reset state.
Note:
The stacking corresponding to an eventual interrupt to leave WAIT mode will only be
executed when leaving WAIT mode.
The following list summarizes the effect of WAIT mode on the modules of the MC68HC05B6.
– The watchdog timer functions according to the mask option selected; refer
to Section 9.1.4.2
– The EEPROM is not affected; refer to Section 3.7
– The SCI is not affected; refer to Section 6.14
– The timer is not affected; refer to Section 5.7
– The PLM is not affected; refer to Section 7.4
– The A/D converter is not affected; refer to Section 8.4
– The I-bit in the CCR is cleared
2.4.2.1 Power consumption during WAIT mode
Power consumption during WAIT mode depends on how many systems are active. The power
consumption will be highest when all the systems (A/D, timer, EEPROM and SCI) are active, and
lowest when the EEPROM erase and programming mechanism, SCI and A/D are disabled. The
timer cannot be disabled in WAIT mode. It is important that before entering WAIT mode, the
programmer sets the relevant control bits for the individual modules to reflect the desired
functionality during WAIT mode.
Power consumption may be further reduced by the use of SLOW mode.
Freescale
2-8
MODES OF OPERATION AND PIN DESCRIPTIONS
MC68HC05B6
Rev. 4.1