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11.5.4 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
should do the following:
1. Mask keyboard interrupts by clearing KBIx_SC[KBIE].
2. Enable the KBI polarity by setting the appropriate KBIx_ES[KBEDGn] bits.
3. Before using internal pullup resistors, configure the associated bits in PORT_PTxPE.
4. Enable the KBI pins by setting the appropriate KBIx_PE[KBIPEn] bits.
5. Write to KBIx_SC[KBACK] to clear any false interrupts.
6. Set KBIx_SC[KBIE] to enable interrupts.
Chapter 11 Keyboard Interrupts (KBI)
MC9S08PA4 Reference Manual, Rev. 5, 08/2017
NXP Semiconductors
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Summary of Contents for MC9S08PA4
Page 1: ...MC9S08PA4 Reference Manual Supports MC9S08PA4 Document Number MC9S08PA4RM Rev 5 08 2017 ...
Page 2: ...MC9S08PA4 Reference Manual Rev 5 08 2017 2 NXP Semiconductors ...
Page 22: ...MC9S08PA4 Reference Manual Rev 5 08 2017 22 NXP Semiconductors ...
Page 28: ...System clock distribution MC9S08PA4 Reference Manual Rev 5 08 2017 28 NXP Semiconductors ...
Page 150: ...Port data registers MC9S08PA4 Reference Manual Rev 5 08 2017 150 NXP Semiconductors ...
Page 196: ...Human machine interfaces HMI MC9S08PA4 Reference Manual Rev 5 08 2017 196 NXP Semiconductors ...
Page 224: ...Instruction Set Summary MC9S08PA4 Reference Manual Rev 5 08 2017 224 NXP Semiconductors ...
Page 232: ...Functional Description MC9S08PA4 Reference Manual Rev 5 08 2017 232 NXP Semiconductors ...
Page 258: ...FTM Interrupts MC9S08PA4 Reference Manual Rev 5 08 2017 258 NXP Semiconductors ...
Page 294: ...Functional description MC9S08PA4 Reference Manual Rev 5 08 2017 294 NXP Semiconductors ...
Page 398: ...Resets MC9S08PA4 Reference Manual Rev 5 08 2017 398 NXP Semiconductors ...
Page 400: ...MC9S08PA4 Reference Manual Rev 5 08 2017 400 NXP Semiconductors ...