HCS08 datasheet(141/198 Pages) NXP

141 / 198 page

Keyboard Interrupts (S08KBIV2)

MC9S08QD4 Series MCU Data Sheet, Rev. 6

Freescale Semiconductor

141

KBISC provided all enabled keyboard inputs are at their deasserted levels. KBF will remain set if any

enabled KBI pin is asserted while attempting to clear by writing a 1 to KBACK.

10.4.3

KBI Pullup/Pulldown Resistors

The KBI pins can be configured to use an internal pullup/pulldown resistor using the associated I/O port

pullup enable register. If an internal resistor is enabled, the KBIES register is used to select whether the

resistor is a pullup (KBEDGn = 0) or a pulldown (KBEDGn = 1).

10.4.4

KBI Initialization

When a keyboard interrupt pin is first enabled it is possible to get a false keyboard interrupt flag. To

prevent a false interrupt request during keyboard initialization, the user must do the following:

1. Mask keyboard interrupts by clearing KBIE in KBISC.

2. Enable the KBI polarity by setting the appropriate KBEDGn bits in KBIES.

3. If using internal pullup/pulldown device, configure the associated pullup enable bits in PTxPE.

4. Enable the KBI pins by setting the appropriate KBIPEn bits in KBIPE.

5. Write to KBACK in KBISC to clear any false interrupts.

6. Set KBIE in KBISC to enable interrupts.

HCS08 Scheda tecnica(PDF) 141 Page - NXP Semiconductors