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Setting a column open-drain enable bit (KCO[7:0]) disables the pull-up driver on that
pin. Clearing the bit allows the pin to drive to the high state. This bit has no effect
when the pin is configured as an input.
Setting a row enable control bit in this register enables the corresponding row line to
participate in interrupt generation. Likewise, clearing a bit disables that row from
being used to generate an interrupt. This register is cleared by reset, disabling all
rows. The row enable logic is independent of the programmed direction of the pin.
Writing a zero to the data register of pins configured as outputs causes a keypad
interrupt to be generated if the row enable associated with that bit is set. It is up to the
programmer to ensure that pins being used for functions other than the keypad are
properly disabled.
The KPCR register is byte or halfword addressable.
KPCR — Keypad Control Register
15
14
13
12
R
KCO7 KCO6 KCO5 KCO4 KCO3 KCO2 KCO1 KCO0 KRE7 KRE6 KRE5 KRE4 KRE3 KRE2 KRE1 KRE0
W
RESET:
0
0
0
0
KCOx — Keypad Column Strobe Open-Drain Enable x
0 = Column strobe output x is totem-pole drive (P-channel enabled).
1 = Column strobe output x is open drain (P-channel disabled).
KREx — Keypad Row Enable x
0 = Row x is not included in keypad key press detect.
1 = Row x is included in keypad key press detect.
14.3.2 Keypad Status Register (KPSR)
The keypad status register (KPSR) reflects the state of the keypress detect circuit.
The keypad key depress (KPKD) status bit is set when one or more enabled rows are
detected low after synchronization. The KPKD status bit remains set until cleared by
software. The KPKD bit may be used to generate a maskable key depress interrupt. If
desired, software may clear the keypress synchronizer chain to allow a repeated
interrupt to be generated while a key remains pressed. In this case, a new interrupt
will be generated after the synchronizer delay elapses if a key remains pressed.
The keypad key release (KPKR) status bit is set when all enabled rows are detected
high after synchronization. The KPKR status bit remains set until cleared by software.
The bit will typically not be set again until the detect circuit senses a key depressed
followed by all keys released. The KPKR bit may be used to generate a maskable key
release interrupt. The key release synchronizer may be set high by software after
scanning the keypad to ensure a known state.
MMC2001
REFERENCE MANUAL
Freescale Semiconductor, Inc.
11
10
9
8
0
0
0
0
Figure 14-2 Keypad Control Register
KEYPAD PORT
For More Information On This Product,
Go to: www.freescale.com
7
6
5
4
0
0
0
0
10003000
3
2
1
0
0
0
0
0
MOTOROLA
14-3
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