Datasheet

Keyboard Interrupt Module (KBI)
Functional Description
MC68HC908QY4•MC68HC908QT4•MC68HC908QY2•MC68HC908QT2•MC68HC908QY1•MC68HC908QT1
MOTOROLA Keyboard Interrupt Module (KBI) 181
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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 input 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 then read the data
register.
NOTE: 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 logic 0 for
software to read the pin.
Auto wake-up latch, AWUL, can be read directly from the bit 6 position
of port A data register (PTA). This is a read-only bit which is occupying
and empty bit position on PTA. No PTA associated registers, such as
PTA6 data, PTA6 direction, and PTA6 pullup exist for this bit.
14.4.1 Keyboard Initialization
When a keyboard interrupt pin is enabled, it takes time for the internal
pullup to reach a logic 1. Therefore a false interrupt can occur as soon
as the pin is enabled. This does not apply to an auto wake-up interrupt,
which is internally generated without pullup.