PIC18F2220 MICROCHIP [Microchip Technology], PIC18F2220 Datasheet - Page 229

• Manufacturer Part Number: PIC18F2220
• Description: 28/40/44-Pin High-Performance, Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology
• Manufacturer: MICROCHIP [Microchip Technology]

21.0
The comparator voltage reference is a 16-tap resistor
ladder network that provides a selectable voltage refer-
ence. The resistor ladder is segmented to provide two
ranges of CV
tion to conserve power when the reference is not being
used. The CVRCON register controls the operation of
the reference as shown in Register 21-1. The block
diagram is given in Figure 21-1.
The comparator reference supply voltage comes from
V
REGISTER 21-1:
 2003 Microchip Technology Inc.
DD
and V
COMPARATOR VOLTAGE
REFERENCE MODULE
SS
bit 7
bit 6
bit 5
bit 4
bit 3-0
.
REF
values and has a power-down func-
CVRCON REGISTER
bit 7
CVREN: Comparator Voltage Reference Enable bit
1 = CV
0 = CV
CVROE: Comparator V
1 = CV
0 = CV
CVRR: Comparator V
1 = 0.00 V
0 = 0.25 V
Unimplemented: Read as ‘0’
CVR3:CVR0: Comparator V
When CVRR = 1:
CV
When CVRR = 0:
CV
Legend:
R = Readable bit
- n = Value at POR
CVREN
R/W-0
Note 1: CVROE overrides the TRISA<2> bit setting.
REF
REF
= (CVR<3:0>)
= 1/4 (CV
REF
REF
REF
REF
DD
DD
voltage is disconnected from the RA2/AN2/V
circuit powered on
circuit powered down
voltage level is also output on the RA2/AN2/V
CVROE
R/W-0
to 0.75 V
to 0.75 V
RSRC
PIC18F2220/2320/4220/4320
REF
REF
DD
DD
) + (CVR<3:0> + 8)
V
R/W-0
CVRR
Range Selection bit
, with V
, with V
24
DD
Output Enable bit
REF
W = Writable bit
‘1’ = Bit is set
Value Selection 0
DD
DD
/24 step size
/32 step size
U-0
—
21.1
The comparator voltage reference can output 16 distinct
voltage levels for each range. The equations used to cal-
culate the output of the comparator voltage reference
are as follows:
EQUATION 21-1:
The settling time of the comparator voltage reference
must be considered when changing the CV
output (see Table 26-2 in Section 26.0 “Electrical
Characteristics”).
V
32
DD
Configuring the Comparator
Voltage Reference
R/W-0
CVR3
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
If CVRR = 1:
CV
If CVRR = 0:
CV
VR3:VR0
REF
REF
REF
REF
= (CVR<3:0>)
= (CVR<3:0> + 8)
-/CV
-/CV
R/W-0
CVR2
15 bits
REF
REF
pin
(1)
pin
x = Bit is unknown
R/W-0
CVR1
V
DS39599C-page 227
24
DD
V
32
DD
R/W-0
CVR0
bit 0
REF