p89lpc9401 NXP Semiconductors, p89lpc9401 Datasheet - Page 35

• Manufacturer Part Number: p89lpc9401
• Description: 8-bit Microcontroller With Accelerated Two-clock 80c51 Core 8 Kb 3 V Byte-erasable Flash With 32 Segment X 4 Lcd Driver
• Manufacturer: NXP Semiconductors

Philips Semiconductors
P89LPC9401_1
Preliminary data sheet
7.23 Keypad interrupt
If a comparator interrupt is enabled (except in Total Power-down mode), a change of the
comparator output state will generate an interrupt and wake-up the processor. If the
comparator output to a pin is enabled, the pin should be configured in the push-pull mode
in order to obtain fast switching times while in Power-down mode. The reason is that with
the oscillator stopped, the temporary strong pull-up that normally occurs during switching
on a quasi-bidirectional port pin does not take place.
Comparators consume power in Power-down and Idle modes, as well as in the normal
operating mode. This fact should be taken into account when system power consumption
is an issue. To minimize power consumption, the user can disable the comparators via
PCONA.5, or put the device in Total Power-down mode.
The Keypad Interrupt (KBI) function is intended primarily to allow a single interrupt to be
generated when Port 0 is equal to or not equal to a certain pattern. This function can be
used for bus address recognition or keypad recognition. The user can configure the port
via SFRs for different tasks.
The Keypad Interrupt Mask Register (KBMASK) is used to define which input pins
connected to Port 0 can trigger the interrupt. The Keypad Pattern Register (KBPATN) is
used to define a pattern that is compared to the value of Port 0. The Keypad Interrupt Flag
(KBIF) in the Keypad Interrupt Control Register (KBCON) is set when the condition is
matched while the Keypad Interrupt function is active. An interrupt will be generated if
enabled. The PATN_SEL bit in the Keypad Interrupt Control Register (KBCON) is used to
define equal or not-equal for the comparison.
In order to use the Keypad Interrupt as an original KBI function like in 87LPC76x series,
the user needs to set KBPATN = 0FFH and PATN_SEL = 1 (not equal), then any key
connected to Port 0 which is enabled by the KBMASK register will cause the hardware to
set KBIF and generate an interrupt if it has been enabled. The interrupt may be used to
wake-up the CPU from Idle or Power-down modes. This feature is particularly useful in
handheld, battery-powered systems that need to carefully manage power consumption
yet also need to be convenient to use.
In order to set the flag and cause an interrupt, the pattern on Port 0 must be held longer
than six CCLKs.
8-bit two-clock 80C51 microcontroller with 32 segment
Rev. 01 — 5 September 2005
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
P89LPC9401
4 LCD driver
35 of 59