P89LPC9331FDH datasheet(51/93 Pages) NXP

51 / 93 page

P89LPC9331_9341_9351_9361_3

Product data sheet

Rev. 03 — 2 June 2009

51 of 93

NXP Semiconductors

P89LPC9331/9341/9351/9361

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

7.26 Analog comparators

Two analog comparators are provided on the P89LPC9331/9341/9351/9361. Input and

output options allow use of the comparators in a number of different conﬁgurations.

Comparator operation is such that the output is a logical one (which may be read in a

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.

In P89LPC9351/9361, the positive inputs of comparators could be ampliﬁed by

Programmable Gain Ampliﬁer 1 (PGA1) module. The PGA1 can supply gain factors of 2x,

4x, 8x, or 16x, eliminating the need for external op-amps in the end application.

The overall connections to both comparators are shown in Figure 20 and Figure 21. The

comparators function to VDD = 2.4 V.

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

guaranteed to be stable for 10

µs. The corresponding comparator interrupt should not be

enabled during that time, and the comparator interrupt ﬂag must be cleared before the

interrupt is enabled in order to prevent an immediate interrupt service.

When a comparator is disabled the comparator’s output, COn, goes HIGH. If the

comparator output was LOW and then is disabled, the resulting transition of the

comparator output from a LOW to HIGH state will set the comparator ﬂag, CMFn. This will

cause an interrupt if the comparator interrupt is enabled. The user should therefore

disable the comparator interrupt prior to disabling the comparator. Additionally, the user

should clear the comparator ﬂag, CMFn, after disabling the comparator.

Fig 19. SPI single master multiple slaves conﬁguration

002aaa903

master

slave

8-BIT SHIFT

SPI CLOCK

GENERATOR

8-BIT SHIFT

MISO

MOSI

SPICLK

port

MISO

MOSI

SPICLK

slave

8-BIT SHIFT

MISO

MOSI

SPICLK

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