P89LPC952FA,512

P89LPC952_954_4 © NXP B.V. 2008. All rights reserved.

Product data sheet Rev. 04 — 24 July 2008 40 of 69

operation is such that the output is a logical one (which may be read in a register and/or

routed to a pin) when the positive input (one of two selectable pins) is greater than the

negative input (selectable from a pin or an internal reference voltage). Otherwise the

output is a zero. Each comparator may be configured to cause an interrupt when the

output value changes.

The overall connections to both comparators are shown in Figure 15. The comparators

function to V

= 2.4 V.

When each comparator is first enabled, the comparator output and interrupt flag are not

P89LPC952_954_4 © NXP B.V. 2008. All rights reserved.

Product data sheet Rev. 04 — 24 July 2008 41 of 69

An internal reference voltage generator may supply a default reference when a single

comparator input pin is used. The value of the internal reference voltage, referred to as

V

ref(bg)

Each comparator has an interrupt flag contained in its configuration register. This flag is

set whenever the comparator output changes state. The flag may be polled by software or

may be used to generate an interrupt. The two comparators use one common interrupt

vector. If both comparators enable interrupts, after entering the interrupt service routine,

the user needs to read the flags to determine which comparator caused the interrupt.

If a comparator interrupt is enabled (except in Total Power-down mode), a change of the

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.