Auto Wakeup Module (AWU)
Wait Mode
MC68HLC908QY/QT Family — Rev. 2
Data Sheet
MOTOROLA
Auto Wakeup Module (AWU)
49
The overflow count can be selected from two options defined by the COPRS bit in
CONFIG1. This bit was “borrowed” from the computer operating properly (COP)
using the fact that the COP feature is idle (no MCU clock available) in stop mode.
The typical values of the periodic wakeup request are (at room temperature):
COPRS = 0: 875 ms @ 3.0 V, 1.1 s @ 2.3 V
COPRS = 1: 22 ms @ 3.0 V, 27 ms @ 2.3 V
The auto wakeup RC oscillator is highly dependent on operating voltage and
temperature. This feature is not recommended for use as a time-keeping function.
The wakeup request is latched to allow the interrupt source identification. The
latched value, AWUL, can be read directly from the bit 6 position of PTA data
register. This is a read-only bit which is occupying an empty bit position on PTA.
No PTA associated registers, such as PTA6 data, PTA6 direction, and PTA6 pullup
exist for this bit. The latch can be cleared by writing to the ACKK bit in the KBSCR
register. Reset also clears the latch. AWUIE bit in KBI interrupt enable register (see
The AWU oscillator and counters are inactive in normal operating mode and
become active only upon entering stop mode.
4.4 Wait Mode
The AWU module remains inactive in wait mode.
4.5 Stop Mode
When the AWU module is enabled (AWUIE = 1 in the keyboard interrupt enable
register) it is activated automatically upon entering stop mode. Clearing the
IMASKK bit in the keyboard status and control register enables keyboard interrupt
requests to bring the MCU out of stop mode. The AWU counters start from ‘0’ each
time stop mode is entered.
4.6 Input/Output Registers
The AWU shares registers with the keyboard interrupt (KBI) module and the port A
I/O module. The following I/O registers control and monitor operation of the AWU:
Port A data register (PTA)
Keyboard interrupt status and control register (KBSCR)
Keyboard interrupt enable register (KBIER)
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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