P89LPC938 NXP Semiconductors, P89LPC938 Datasheet - Page 40

• Manufacturer Part Number: P89LPC938
• Description: The P89LPC938 is a single-chip microcontroller, available in low cost packages, based ona high performance processor architecture that executes instructions in two to four clocks,six times the rate of standard 80C51 devices
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 14051
Product data sheet
Fig 19. Comparator input and output connections.
(P0.5) CMPREF
(P0.4) CIN1A
(P0.3) CIN1B
(P0.2) CIN2A
(P0.1) CIN2B
7.23.1 Internal reference voltage
7.23.2 Comparator interrupt
7.23.3 Comparators and power reduction modes
7.23 Analog comparators
V
REF
Two analog comparators are provided on the P89LPC938. 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 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
function to V
When each comparator is first enabled, the comparator output and interrupt flag are not
guaranteed to be stable for 10 microseconds. 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.
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
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.
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.
REF
, is 1.23 V
CN1
CN2
CP1
CP2
DD
= 2.4 V.
10 %.
comparator 1
comparator 2
Rev. 01 — 25 February 2005
CO1
CO2
change detect
change detect
OE1
OE2
8-bit microcontroller with 10-bit A/D converter
CMF1
CMF2
CMP1 (P0.6)
CMP2 (P0.0)
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
Figure
002aaa904
P89LPC938
19. The comparators
EC
interrupt
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