P89LPC913 datasheet(44/63 Pages) PHILIPS

44 / 63 page

Philips Semiconductors

P89LPC912/913/914

8-bit microcontrollers with two-clock 80C51 core

Product data

Rev. 03 — 17 December 2004

44 of 63

9397 750 14468

9.22 Comparator 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.

9.23 Keypad interrupt (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.

CN1, OE1=00

CN1, OE1 = 0 1

CN1, OE1=10

CN1, OE1 = 1 1

CN2=0

CN2=1

Fig 22. Comparator conﬁgurations.

CIN1A

CMPREF

002aaa490

CO1

CIN1A

CMPREF

002aaa491

CO1

CMP1

CIN1A

VREF (1.23 V)

002aaa492

CO1

CIN1A

VREF (1.23 V)

002aaa493

CO1

CMP1

CIN2A

CMPREF

002aaa494

CO2

CIN2A

VREF (1.23 V)

002aaa495

CO2

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