PIC18F2420-I/SOC01 Microchip, PIC18F2420-I/SOC01 Datasheet - Page 241
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PIC18F2420-I/SOC01
Manufacturer Part Number
PIC18F2420-I/SOC01
Description
28 pin, 16 kb flash, 3804 ram, 25 i/o...
Manufacturer
Microchip
Datasheet
1.PIC18F2420-ISOC01.pdf
(412 pages)
- Current page: 241 of 412
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21.0
The comparator voltage reference is a 16-tap resistor
ladder network that provides a selectable reference
voltage. Although its primary purpose is to provide a
reference for the analog comparators, it may also be
used independently of them.
A block diagram of the module is shown in Figure 21-1.
The resistor ladder is segmented to provide two ranges
of CV
conserve power when the reference is not being used.
The module’s supply reference can be provided from
either device V
21.1
The voltage reference module is controlled through the
CVRCON register (Register 21-1). The comparator
voltage reference provides two ranges of output volt-
age, each with 16 distinct levels. The range to be used
REGISTER 21-1:
© 2008 Microchip Technology Inc.
bit 7
Legend:
R = Readable bit
-n = Value at POR
bit 7
bit 6
bit 5
bit 4
bit 3-0
Note 1:
CVREN
R/W-0
REF
COMPARATOR VOLTAGE
REFERENCE MODULE
Configuring the Comparator
Voltage Reference
values and has a power-down function to
CVROE overrides the TRISA<2> bit setting.
DD
CVREN: Comparator Voltage Reference Enable bit
1 = CV
0 = CV
CVROE: Comparator V
1 = CV
0 = CV
CVRR: Comparator V
1 = 0 to 0.667 CV
0 = 0.25 CV
CVRSS: Comparator V
1 = Comparator reference source, CV
0 = Comparator reference source, CV
CVR3:CVR0: Comparator V
When CVRR = 1:
CV
When CVRR = 0:
CV
CVROE
/V
REF
REF
R/W-0
SS
or an external voltage reference.
CVRCON: COMPARATOR VOLTAGE REFERENCE CONTROL REGISTER
= ((CVR<3:0>)/24) • (CV
= (CV
REF
REF
REF
REF
(1)
voltage is disconnected from the RA2/AN2/V
circuit powered on
circuit powered down
voltage level is also output on the RA2/AN2/V
RSRC
RSRC
W = Writable bit
‘1’ = Bit is set
R/W-0
CVRR
/4) + ((CVR<3:0>)/32) • (CV
RSRC
to 0.75 CV
REF
REF
REF
, with CV
Range Selection bit
Source Selection bit
Output Enable bit
REF
RSRC
PIC18F2420/2520/4420/4520
RSRC
CVRSS
RSRC
Value Selection bits (0 ≤ (CVR<3:0>) ≤ 15)
R/W-0
, with CV
)
/24 step size (low range)
RSRC
RSRC
RSRC
= (V
= V
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
(1)
RSRC
R/W-0
DD
CVR3
is selected by the CVRR bit (CVRCON<5>). The
primary difference between the ranges is the size of the
steps
(CVR<3:0>), with one range offering finer resolution.
The equations used to calculate the output of the
comparator voltage reference are as follows:
The comparator reference supply voltage can come
from either V
V
voltage source is selected by the CVRSS bit
(CVRCON<4>).
The settling time of the comparator voltage reference
must be considered when changing the CV
put (see Table 26-3 in Section 26.0 “Electrical
Characteristics”).
/32 step size (high range)
REF
REF
– V
)
+) – (V
If CVRR = 1:
CV
If CVRR = 0:
CV
CV
- that are multiplexed with RA2 and RA3. The
SS
REF
REF
RSRC
selected
REF
REF
REF
= ((CVR<3:0>)/24) x CV
= (CV
-/CV
)
-/CV
DD
-)
R/W-0
CVR2
REF
and V
REF
RSRC
by
pin
pin
SS
x 1/4) + (((CVR<3:0>)/32) x
the
, or the external V
x = Bit is unknown
R/W-0
CVR1
CV
REF
DS39631E-page 239
RSRC
Selection
R/W-0
CVR0
REF
REF
+ and
bit 0
out-
bits
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