P89LPC920FDH PHILIPS [NXP Semiconductors], P89LPC920FDH Datasheet - Page 28

• Manufacturer Part Number: P89LPC920FDH
• Description: 8-bit microcontrollers with two-clock 80C51 core 2 kB/4 kB/8 kB 3 V low-power Flash with 256-byte data RAM
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
9397 750 11945
Product data
Fig 10. Comparator input and output connections.
(P0.5) CMPREF
(P0.4) CIN1A
(P0.3) CIN1B
(P0.2) CIN2A
(P0.1) CIN2B
V REF
8.20.1 Internal reference voltage
8.20.2 Comparator interrupt
8.20 Analog comparators
Two analog comparators are provided on the P89LPC920/921/922. 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
comparators 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.
REF
, is 1.23 V 10%.
CP1
CN1
CP2
CN2
Rev. 04 — 09 September 2003
Comparator 1
Comparator 2
DD
CO1
CO2
= 2.4 V.
Change Detect
Change Detect
8-bit microcontrollers with two-clock 80C51 core
OE1
OE2
P89LPC920/921/922
CMF1
CMF2
© Koninklijke Philips Electronics N.V. 2003. All rights reserved.
CMP1 (P0.6)
CMP2 (P0.0)
Figure
EC
002aaa422
10. The
Interrupt
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