s908ey8ad4cfjer Freescale Semiconductor, Inc, s908ey8ad4cfjer Datasheet - Page 107

• Manufacturer Part Number: s908ey8ad4cfjer
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

The vector fetch or software clear and the return of all enabled keyboard interrupt pins to logic 1 may occur
in any order.
If the MODEK bit is clear, the keyboard interrupt pin is falling edge-sensitive only. With MODEK clear, a
vector fetch or software clear immediately clears the keyboard interrupt request.
Reset clears the keyboard interrupt request and the MODEK bit, clearing the interrupt request even if a
keyboard interrupt pin stays at logic 0.
The keyboard flag bit (KEYF) in the keyboard status and control register can be used to see if a pending
interrupt exists. The KEYF bit is not affected by the keyboard interrupt mask bit (IMASKK) which makes
it useful in applications where polling is preferred.
To determine the logic level on a keyboard interrupt pin, use the data direction register to configure the
pin as an input and read the data register.
Freescale Semiconductor
TO PULLUP
TO PULLUP
ENABLE
ENABLE
KBD0
KBD4
KB0IE
KB4IE
Setting a keyboard interrupt enable bit (KBIEx) forces the corresponding
keyboard interrupt pin to be an input, overriding the data direction register.
However, the data direction register bit must be a 0 for software to read the
pin.
.
.
.
Figure 10-2. Keyboard Module Block Diagram
MC68HC908EY16 • MC68HC908EY8 Data Sheet, Rev. 10
MODEK
V
DD
D
CK
NOTE
CLR
Q
INTERRUPT FF
KEYBOARD
RESET
ACKK
IMASKK
SYNCHRONIZER
VECTOR FETCH
INTERNAL BUS
DECODER
Functional Description
KEYF
KEYBOARD
INTERRUPT
REQUEST
107