mc68hc908qf4 Freescale Semiconductor, Inc, mc68hc908qf4 Datasheet - Page 46

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

Auto Wakeup Module (AWU)
4.3 Functional Description
Data Sheet
46
(CGMXCLK)
BUSCLKX4
RESET
CLK
CLRLOGIC
Figure 4-2. Auto Wakeup Interrupt Request Generation Logic
COPRS (FROM CONFIG1)
RST
CLEAR
EN
The function of the auto wakeup logic is to generate periodic wakeup requests to
bring the microcontroller unit (MCU) out of stop mode. The wakeup requests are
treated as regular keyboard interrupt requests, with the difference that instead of a
pin, the interrupt signal is generated by an internal logic.
Writing the AWUIE bit in the keyboard interrupt enable register enables or disables
the auto wakeup interrupt input (see
AWUIREQ input with auto wakeup interrupt request enabled, latches an auto
wakeup interrupt request.
Auto wakeup latch, AWUL, can be read directly from the bit 6 position of port A data
register (PTA). This is a read-only bit which is occupying an empty bit position on
PTA. No PTA associated registers, such as PTA6 data direction or PTA6 pullup
exist for this bit.
Entering stop mode will enable the auto wakeup generation logic. An internal RC
oscillator (exclusive for the auto wakeup feature) drives the wakeup request
generator. Once the overflow count is reached in the generator counter, a wakeup
request, AWUIREQ, is latched and sent to the KBI logic. See
Wakeup interrupt requests will only be serviced if the associated interrupt enable
bit, AWUIE, in KBIER is set. The AWU shares the keyboard interrupt vector.
INT RC OSC
32 kHz
Freescale Semiconductor, Inc.
For More Information On This Product,
RESET
AWUIE
SHORT
CLK
AUTOWUGEN
Go to: www.freescale.com
Auto Wakeup Module (AWU)
ISTOP
OVERFLOW
RST
1 = DIV 2
0 = DIV 2
9
14
RESET
Figure
ACKK
V
4-2). A logic 1 applied to the
DD
D
E
R
Q
MC68HC908QF4 — Rev. 1.0
TO KBI INTERRUPT LOGIC (SEE
Figure 9-3. Keyboard Interrupt
Block
Figure
TO PTA READ, BIT 6
Diagram)
4-1.
MOTOROLA
AWUIREQ
AWUL