mc68hc908qf4 Freescale Semiconductor, Inc, mc68hc908qf4 Datasheet - Page 47

• Manufacturer Part Number: mc68hc908qf4
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

4.4 Wait Mode
4.5 Stop Mode
4.6 Input/Output Registers
MC68HC908QF4 — Rev. 1.0
MOTOROLA
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):
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
Figure
The AWU oscillator and counters are inactive in normal operating mode and
become active only upon entering stop mode.
The AWU module remains inactive in wait 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.
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:
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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
Port A data register (PTA)
Keyboard interrupt status and control register (KBSCR)
Keyboard interrupt enable register (KBIER)
Freescale Semiconductor, Inc.
4-2) has no effect on AWUL reading.
For More Information On This Product,
Go to: www.freescale.com
Auto Wakeup Module (AWU)
Auto Wakeup Module (AWU)
Wait Mode
Data Sheet
47