Datasheet

MC68HC908QB8 Data Sheet, Rev. 3
Freescale Semiconductor 51
Chapter 4
Auto Wakeup Module (AWU)
4.1 Introduction
This section describes the auto wakeup module (AWU). The AWU generates a periodic interrupt during
stop mode to wake the part up without requiring an external signal. Figure 4-1 is a block diagram of the
AWU.
Figure 4-1. Auto Wakeup Interrupt Request Generation Logic
4.2 Features
Features of the auto wakeup module include:
• One internal interrupt with separate interrupt enable bit, sharing the same keyboard interrupt vector
and keyboard interrupt mask bit
• Exit from low-power stop mode without external signals
• Selectable timeout periods
• Dedicated low-power internal oscillator separate from the main system clock sources
• Option to allow bus clock source to run the AWU if enabled in STOP
D
R
V
DD
INT RC OSC
EN 32 kHz
CLK
RST
OVERFLOW
AUTOWUGEN
SHORT
COPRS (FROM CONFIG1)
1 = DIV 2
9
0 = DIV 2
14
E
RESET
ACKK
CLEAR
RST
RESET
CLK
BUSCLKX2
ISTOP
AWUIREQ
CLRLOGIC
RESET
AWUL
TO PTA READ, BIT 6
Q
AWUIE
TO KBI INTERRUPT LOGIC
(SEE Figure 9-2)
BUSCLKX2
OSCENINSTOP (FROM CONFIG2)
M
U
X