PIC18F6621-I/PT Microchip Technology Inc., PIC18F6621-I/PT Datasheet - Page 251

• Manufacturer Part Number: PIC18F6621-I/PT
• Description: 64 PIN, 64 KB FLASH, 3840 RAM, 52 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC18F6621-I/PT

• A/d Inputs: 12-Channel, 10-Bit
• Comparators: 2
• Cpu Speed: 10 MIPS
• Eeprom Memory: 1024 Bytes
• Input Output: 54
• Interface: I2C/SPI/UART/USART
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 64-pin TQFP
• Programmable Memory: 64K Bytes
• Ram Size: 3.8K 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 Electrostatic Device

22.0
The comparator voltage reference is a 16-tap resistor
ladder network that provides a selectable voltage
reference. The resistor ladder is segmented to provide
two ranges of CV
function to conserve power when the reference is not
being used.
operation of the reference as shown in Register 22-1.
The block diagram is given in Figure 22-1.
The comparator reference supply voltage can come
from either V
V
comparator reference supply voltage is controlled by
the CVRSS bit.
REGISTER 22-1:
 2005 Microchip Technology Inc.
REF
- that are multiplexed with RA3 and RA2. The
COMPARATOR VOLTAGE
REFERENCE MODULE
bit 7
bit 6
bit 5
bit 4
bit 3-0
DD
The CVRCON register controls the
and V
REF
CVRCON: COMPARATOR VOLTAGE REFERENCE CONTROL REGISTER
values and has a power-down
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
bit 7
SS
Legend:
R = Readable bit
-n = Value at POR
CVREN
R/W-0
Note 1: If enabled for output, RF5 must also be configured as an input by setting TRISF<5>
, or the external V
REF
REF
= (CVR<3:0>/ 24) • (CV
= 1/4 • (CV
REF
REF
REF
REF
to ‘1’.
circuit powered on
circuit powered down
voltage level is also output on the RF5/AN10/CV
voltage is disconnected from the RF5/AN10/CV
CVROE
RSRC
RSRC
R/W-0
to 0.667 CV
to 0.75 CV
RSRC
(1)
REF
REF
PIC18F6525/6621/8525/8621
REF
REF
) + (CVR3:CVR0/32) • (CV
+ and
Range Selection bit
R/W-0
CVRR
Source Selection bit
Output Enable bit
REF
W = Writable bit
‘1’ = Bit is set
RSRC
RSRC
RSRC
Value Selection bits (0 ≤ VR3:VR0 ≤ 15)
, with CV
, with CV
)
CVRSS
R/W-0
RSRC
RSRC
22.1
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 27.0 “Electrical Characteristics”).
RSRC
= V
= AV
RSRC
If CVRR = 1:
CV
If CVRR = 0:
CV
(1)
REF
REF
REF
/32 step size (high range)
DD
/24 step size (low range)
Configuring the Comparator
Voltage Reference
R/W-0
CVR3
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
RSRC
+ – V
= (CV
– AV
= (CVR<3:0>/24) x CV
)
REF
SS
RSRC
REF
-
REF
R/W-0
CVR2
x 1/4) + (CVR<3:0>/32) x CV
pin
pin
x = Bit is unknown
R/W-0
CVR1
RSRC
DS39612B-page 249
REF
R/W-0
CVR0
output
RSRC
bit 0