p89lpc9351 NXP Semiconductors, p89lpc9351 Datasheet - Page 43

• Manufacturer Part Number: p89lpc9351
• Description: 8-bit Microcontroller With Accelerated Two-clock 80c51 Core 8 Kb 3 V Byte-erasable ?ash With 8-bit Adc
• Manufacturer: NXP Semiconductors

NXP Semiconductors
P89LPC9351_1
Preliminary data sheet
7.26 Analog comparators
Two analog comparators are provided on the P89LPC9351. 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 register and/or routed to a
pin) when the positive input (one of two selectable inputs) 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 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
function to V
When each comparator is first enabled, the comparator output and interrupt flag are not
guaranteed to be stable for 10 s. 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 17. SPI single master multiple slaves configuration
GENERATOR
8-BIT SHIFT
SPI CLOCK
REGISTER
DD
master
= 2.4 V.
Rev. 01 — 19 November 2008
MISO
MOSI
SPICLK
port
port
8-bit microcontroller with 8-bit ADC
SPICLK
SPICLK
MISO
MOSI
MISO
MOSI
Figure
SS
SS
P89LPC9351
18. The comparators
8-BIT SHIFT
8-BIT SHIFT
REGISTER
REGISTER
© NXP B.V. 2008. All rights reserved.
slave
slave
002aaa903
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