Datasheet

Keyboard Interrupt Module (KBI)
Functional Description
MC68HC908QY4•MC68HC908QT4•MC68HC908QY2•MC68HC908QT2•MC68HC908QY1•MC68HC908QT1
MOTOROLA Keyboard Interrupt Module (KBI) 185
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14.4.4 Auto Wake-up Interrupt Request
Figure 14-5. Auto Wake-up Interrupt Request Generation Logic
The function of the auto wake-up logic is to generate periodic wake-up
requests to bring the microcontroller unit (MCU) out of stop mode. The
wake-up 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.
Entering stop mode will enable the auto wake-up generation logic. An
internal RC oscillator (exclusive for the auto wake-up feature) drives the
wake-up request generator. Once the overflow count is reached in the
generator counter, a wake-up request, AWUIREQ, is latched and sent to
the KBI logic (see Figure 14-2).
Wake-up interrupt requests will only be serviced if the associated
interrupt enable bit, AWUIE, in KBIER is set.
D
R
V
DD
INT RC OSC
EN
32KHz
CLK
RST
OVERFLOW
AUTOWUGEN
SHORT
COPRS (FROM CONFIG1)
1 = DIV 2
9
0 = DIV 2
14
E
RESET
ACKK
CLEAR
RST
RESET
CLK
(CGMXCLK)
BUSCLKX4
ISTOP
AWUIREQ
CLRLOGIC
RESET
AWUL
TO PTA READ, BIT 6
Q
AWUIE
TO KBI INTERRUPT LOGIC
(SEE Figure 14-2)