PIC18F8520-I/PT Microchip Technology Inc., PIC18F8520-I/PT Datasheet - Page 231

• Manufacturer Part Number: PIC18F8520-I/PT
• Description: 80 PIN, 32 KB FLASH, 2048 RAM, 68 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC18F8520-I/PT

• A/d Inputs: 16-Channel, 10-Bit
• Comparators: 2
• Cpu Speed: 10 MIPS
• Eeprom Memory: 1024 Bytes
• Input Output: 68
• Interface: I2C/SPI/UART/USART
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 80-pin TQFP
• Programmable Memory: 32K Bytes
• Ram Size: 2K Bytes
• Speed: 40 MHz
• Timers: 2-8-bit, 3-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part

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
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 can come
from either V
V
comparator reference supply voltage is controlled by
the CVRSS bit.
REGISTER 21-1:
 2004 Microchip Technology Inc.
REF
Note: In order to select external V
- that are multiplexed with RA3 and RA2. The
COMPARATOR VOLTAGE
REFERENCE MODULE
supply voltages, the Voltage Reference Con-
figuration
ADCON1 register must be set appropriately.
bit 7
bit 6
bit 5
bit 4
bit 3-0
REF
DD
values and has a power-down function
PIC18F6520/8520/6620/8620/6720/8720
or V
bits
SS
CVRCON REGISTER
bit 7
Legend:
R = Readable bit
- n = Value at POR
CVREN: Comparator Voltage Reference Enable bit
1 = CV
0 = CV
CVROE: Comparator V
1 = CV
0 = CV
CVRR: Comparator V
1 = 0.00 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
, or the external V
CVREN
R/W-0
Note 1: If enabled for output, RF5 must also be configured as an input by setting TRISF<5>
(VCFG1:VCFG0)
REF
REF
= (CVR<3:0>/24) (CV
= 1/4 (CV
REF
REF
REF
REF
2: In order to select external V
circuit powered on
circuit powered down
voltage level is also output on the RF5/AN10/CV
voltage is disconnected from the RF5/AN10/CV
to ‘1’.
Reference Configuration bits (VCFG1:VCFG0) of the ADCON1 register must be
set appropriately.
RSRC
RSRC
CVROE
REF
R/W-0
+ and V
to 0.667 CV
to 0.75 CV
RSRC
REF
REF
of
REF
REF
) + (CVR3:CVR0/32) (CV
+ and
REF
R/W-0
CVRR
Range Selection bit
the
Source Selection bit
Output Enable bit
W = Writable bit
‘1’ = Bit is set
REF
-
RSRC
RSRC
RSRC
Value Selection bits (0
, with CV
, with CV
)
CVRSS
R/W-0
RSRC
RSRC
21.1
The comparator voltage reference can output 16 distinct
voltage levels for each range. The equations used to
calculate the output of the comparator voltage reference
are as follows:
The settling time of the comparator voltage reference
must be considered when changing the CV
(Section 26.0 “Electrical Characteristics”).
If CVRR = 1:
CV
If CVRR = 0:
CV
RSRC
= V
= V
REF
RSRC
(1)
REF
REF
REF
DD
+ and V
(2)
/32 step size (high range)
Configuring the Comparator
Voltage Reference
R/W-0
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
CVR3
/24 step size (low range)
= (CVR<3:0>/24) x CV
= (CV
– V
RSRC
+ – V
SS
RSRC
)
REF
REF
VR3:VR0
REF
-
REF
- supply voltages, the Voltage
x 1/4) + (CVR<3:0>/32) x CV
R/W-0
CVR2
pin
pin
15)
RSRC
x = Bit is unknown
R/W-0
CVR1
DS39609B-page 229
REF
R/W-0
CVR0
output
RSRC
bit 0