MC908QY8CDWE Datasheet, PDF (53/232 Pages) Freescale Semiconductor, Inc – Addendum to MC68HC908QB8, rev. 3

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.
COPRS (FROM CONFIG1)
OSCENINSTOP (FROM CONFIG2)
AUTOWUGEN
SHORT
1 = DIV 2⁹
0 = DIV 2¹⁴
BUSCLKX2
OVERFLOW
M
EN 32 kHz
U
X
CLK _RST
INT RC OSC
V_DD
D
Q
E
R
TO PTA READ, BIT 6
AWUL
AWUIREQ
TO KBI INTERRUPT LOGIC
(SEE Figure 9-2)
BUSCLKX2
CLRLOGIC
CLEAR
CLK
RST
RESET _ISTOP
RESET
ACKK
RESET
AWUIE
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
MC68HC908QB8 Data Sheet, Rev. 3
Freescale Semiconductor
51