MC908QY8CDWE Datasheet, PDF (89/232 Pages) Freescale Semiconductor, Inc – Addendum to MC68HC908QB8, rev. 3

I/O Signals
9.7 I/O Signals
The KBI module can share its pins with the general-purpose I/O pins. See Figure 9-1 for the port pins that
are shared.
9.7.1 KBI Input Pins (KBIx:KBI0)
Each KBI pin is independently programmable as an external interrupt source. KBI pin polarity can be
controlled independently. Each KBI pin when enabled will automatically configure the appropriate
pullup/pulldown device based on polarity.
9.8 Registers
The following registers control and monitor operation of the KBI module:
• KBSCR (keyboard interrupt status and control register)
• KBIER (keyboard interrupt enable register)
• KBIPR (keyboard interrupt polarity register)
9.8.1 Keyboard Status and Control Register (KBSCR)
Features of the KBSCR:
• Flags keyboard interrupt requests
• Acknowledges keyboard interrupt requests
• Masks keyboard interrupt requests
• Controls keyboard interrupt triggering sensitivity
Bit 7
Read: 0
Write:
Reset: 0
6
5
0
0
0
0
= Unimplemented
4
3
2
1
Bit 0
0
KEYF
0
IMASKK MODEK
ACKK
0
0
0
0
0
Figure 9-3. Keyboard Status and Control Register (KBSCR)
Bits 7–4 — Not used
KEYF — Keyboard Flag Bit
This read-only bit is set when a keyboard interrupt is pending.
1 = Keyboard interrupt pending
0 = No keyboard interrupt pending
ACKK — Keyboard Acknowledge Bit
Writing a 1 to this write-only bit clears the KBI request. ACKK always reads 0.
IMASKK— Keyboard Interrupt Mask Bit
Writing a 1 to this read/write bit prevents the output of the KBI latch from generating interrupt requests.
1 = Keyboard interrupt requests disabled
0 = Keyboard interrupt requests enabled
MODEK — Keyboard Triggering Sensitivity Bit
This read/write bit controls the triggering sensitivity of the keyboard interrupt pins.
1 = Keyboard interrupt requests on edge and level
0 = Keyboard interrupt requests on edge only
MC68HC908QB8 Data Sheet, Rev. 3
Freescale Semiconductor
87