P89LPC913 datasheet(46/66 Pages) NXP

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P89LPC912_913_914_5

Product data sheet

Rev. 05 — 28 September 2007

46 of 66

NXP Semiconductors

P89LPC912/913/914

8-bit microcontrollers with two-clock 80C51 core

8.23 Comparators and power reduction modes

Either or both comparators may remain enabled when Power-down or Idle mode is

activated, but both comparators are disabled automatically in Total Power-down mode.

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.

8.24 Keypad interrupt

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.

a. CN1, OE1=00

b. CN1, OE1=01

c. CN1, OE1=10

d. CN1, OE1=11

e. CN2=0

f. CN2=1

Fig 22. Comparator conﬁgurations

CIN1A

CMPREF

002aaa490

CO1

CIN1A

CMPREF

002aaa491

CMP1

CO1

CIN1A

VREF (1.23 V)

002aaa492

CO1

CIN1A

VREF (1.23 V)

002aaa493

CMP1

CO1

CIN2A

CMPREF

002aaa494

CO2

CIN2A

VREF (1.23 V)

002aaa495

CO2

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