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Keyboard/External Interrupt Module (KBI)

Data Sheet

MC68HC908RF2 — Rev. 4.0

Keyboard/External Interrupt Module (KBI)

MOTOROLA

Figure 7-5. Keyboard Interrupt Block Diagram

7.3.3 KBI Module During Break Interrupts

The system integration module (SIM) controls whether the IRQ1 or keyboard

interrupt latches can be cleared during the break state. The BCFE bit in the break

flag control register (BFCR) enables software to clear the latches during the break

state. (See 10.7.3 SIM Break Flag Control Register.)

To allow software to clear the IRQ1 or keyboard latches during a break interrupt,

write a 1 to the BCFE bit. If a latch is cleared during the break state, it remains

cleared when the MCU exits the break state.

To protect the latch during the break state, write a 0 to the BCFE bit. With BCFE

at 0 (its default state), writing to the ACKI or ACKK bits in the IRQ and keyboard

status and control register during the break state has no effect on the IRQ1 or

keyboard latches.

7.3.4 Keyboard Interrupt Pins

Writing to the KBIE6–KBIE1 bits in the keyboard interrupt enable register

independently enables or disables each port A pin as a keyboard interrupt pin.

Enabling a keyboard interrupt pin also enables its internal pullup device. A logic 0

applied to an enabled keyboard interrupt pin latches an IRQ1/keyboard interrupt

request.

KB1IE

KB6IE

KEYBOARD

INTERRUPT

CLR

VDD

MODEK

IMASKK

KEYBOARD

INTERRUPT LATCH

REQUEST

VECTOR FETCH

DECODER

ACKK

INTERNAL BUS

RESET

TO PULLUP

KBD6

KBD1

TO PULLUP

SYNCHRONIZER

KEYF

ENABLE

IRQ1

INTERRUPT

REQUEST

IRQ1/KEYBOARD

INTERRUPT

REQUEST

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