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MC908QY2ACPE Datasheet(Hoja de datos) 83 Page - Freescale Semiconductor, Inc

No. de Pieza. MC908QY2ACPE
Descripción  M68HC08 Microcontrollers
Descarga  200 Pages
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Fabricante  FREESCALE [Freescale Semiconductor, Inc]
Página de inicio  http://www.freescale.com
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 83 page
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MC68HC908QYA/QTA Family Data Sheet, Rev. 3
Freescale Semiconductor
83
Chapter 9
Keyboard Interrupt Module (KBI)
9.1 Introduction
The keyboard interrupt module (KBI) provides independently maskable external interrupts.
The KBI shares its pins with general-purpose input/output (I/O) port pins. See Figure 9-1 for port location
of these shared pins.
9.2 Features
Features of the keyboard interrupt module include:
Keyboard interrupt pins with separate keyboard interrupt enable bits and one keyboard interrupt
mask
Programmable edge-only or edge and level interrupt sensitivity
Edge sensitivity programmable for rising or falling edge
Level sensitivity programmable for high or low level
Pullup or pulldown device automatically enabled based on the polarity of edge or level detect
Exit from low-power modes
9.3 Functional Description
The keyboard interrupt module controls the enabling/disabling of interrupt functions on the KBI pins.
These pins can be enabled/disabled independently of each other. See Figure 9-2.
9.3.1 Keyboard Operation
Writing to the KBIEx bits in the keyboard interrupt enable register (KBIER) independently enables or
disables each KBI pin. The polarity of the keyboard interrupt is controlled using the KBIPx bits in the
keyboard interrupt polarity register (KBIPR). Edge-only or edge and level sensitivity is controlled using the
MODEK bit in the keyboard status and control register (KBISCR).
Enabling a keyboard interrupt pin also enables its internal pullup or pulldown device based on the polarity
enabled. On falling edge or low level detection, a pullup device is configured. On rising edge or high level
detection, a pulldown device is configured.
The keyboard interrupt latch is set when one or more enabled keyboard interrupt inputs are asserted.
If the keyboard interrupt sensitivity is edge-only, for KBIPx = 0, a falling (for KBIPx = 1, a rising)
edge on a keyboard interrupt input does not latch an interrupt request if another enabled keyboard
pin is already asserted. To prevent losing an interrupt request on one input because another input
remains asserted, software can disable the latter input while it is asserted.
If the keyboard interrupt is edge and level sensitive, an interrupt request is present as long as any
enabled keyboard interrupt input is asserted.




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