MC68HLC908QY4 Datasheet, PDF (48/182 Pages) Motorola, Inc – Microcontrollers

Auto Wakeup Module (AWU)
COPRS (FROM CONFIG1)
AUTOWUGEN
SHORT
1 = DIV 2⁹
0 = DIV 2¹⁴
INT RC OSC
OVERFLOW
EN 32 kHz
CLK
RST
V_DD
D
Q
TO PTA READ, BIT 6
AWUL
E
R
AWUIREQ
TO KBI INTERRUPT LOGIC (SEE
Figure 9-2. Keyboard Interrupt
Block Diagram)
(CGMXCLK)
BUSCLKX4
RESET
CLRLOGIC
CLEAR
CLK
RST
RESET _ISTOP
RESET
ACKK
AWUIE
Figure 4-1. Auto Wakeup Interrupt Request Generation Logic
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 Figure 4-1) has no effect on AWUL
reading.
The AWU oscillator and counters are inactive in normal operating mode and become active only upon
entering stop mode.
MC68HLC908QY/QT Family Data Sheet, Rev. 3
48
Freescale Semiconductor