P89LPC915FDH datasheet(49/75 Pages) NXP

49 / 75 page

P89LPC915_916_917_5

Product data sheet

Rev. 05 — 15 December 2009

49 of 75

NXP Semiconductors

P89LPC915/916/917

8-bit microcontrollers with accelerated two-clock 80C51 core

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.

8.23 KBI

The Keypad Interrupt 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.

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