MC68HC908GT16_07 FREESCALE [Freescale Semiconductor, Inc], MC68HC908GT16_07 Datasheet - Page 109

• Manufacturer Part Number: MC68HC908GT16_07
• Description: Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

If the MODEK bit is set, the keyboard interrupt pins are both falling edge- and low-level sensitive, and both
of the following actions must occur to clear a keyboard interrupt request:
Freescale Semiconductor
TO PULLUP ENABLE
TO PULLUP ENABLE
$001A
$001B
Addr.
•
•
Vector fetch or software clear — A vector fetch generates an interrupt acknowledge signal to clear
the interrupt request. Software may generate the interrupt acknowledge signal by writing a 1 to the
ACKK bit in the keyboard status and control register (INTKBSCR). The ACKK bit is useful in
applications that poll the keyboard interrupt pins and require software to clear the keyboard
interrupt request. Writing to the ACKK bit prior to leaving an interrupt service routine can also
prevent spurious interrupts due to noise. Setting ACKK does not affect subsequent transitions on
the keyboard interrupt pins. A falling edge that occurs after writing to the ACKK bit latches another
interrupt request. If the keyboard interrupt mask bit, IMASKK, is clear, the CPU loads the program
counter with the vector address at locations $FFE0 and $FFE1.
Return of all enabled keyboard interrupt pins to logic 1 — As long as any enabled keyboard
interrupt pin is at logic 0, the keyboard interrupt remains set.
KBD0
KBD7
Keyboard Interrupt Enable
Register Name
and Control Register
Keyboard Status
KB0IE
KB7IE
See page 111.
See page 112.
(INTKBSCR)
(INTKBIER)
MC68HC908GT16 • MC68HC908GT8 • MC68HC08GT16 Data Sheet, Rev. 5.0
Register
.
.
.
Reset:
Reset:
Read:
Read:
Figure 9-2. Keyboard Module Block Diagram
Write:
Write:
Figure 9-3. I/O Register Summary
KBIE7
Bit 7
0
0
0
= Unimplemented
MODEK
KBIE6
V
6
0
0
0
DD
D
CK
CLR
KBIE5
5
0
0
0
Q
RESET
KBIE4
4
0
0
0
IMASKK
ACKK
KBIE3
KEYF
SYNCHRONIZER
3
0
0
VECTOR FETCH
INTERNAL BUS
ACKK
KBIE2
DECODER
2
0
0
0
KEYF
Functional Description
IMASKK
KBIE1
1
0
0
KEYBOARD
INTERRUPT
REQUEST
MODEK
KBIE0
Bit 0
0
0
109