PIC18F458T-I/PT Microchip Technology, PIC18F458T-I/PT Datasheet - Page 257

• Manufacturer Part Number: PIC18F458T-I/PT
• Description: IC MCU FLASH 16KX16 W/CAN 44TQFP
• Manufacturer: Microchip Technology
• Series: PIC® 18Fr

Specifications of PIC18F458T-I/PT

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 40MHz
• Connectivity: CAN, I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, LVD, POR, PWM, WDT
• Number Of I /o: 33
• Program Memory Size: 32KB (16K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 256 x 8
• Ram Size: 1.5K x 8
• Voltage - Supply (vcc/vdd): 4.2 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-TQFP, 44-VQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

22.0
This module is a 16-tap resistor ladder network that
provides a selectable voltage reference. The resistor
ladder is segmented to provide two ranges of CV
values and has a power-down function to conserve
power when the reference is not being used. The
CVRCON register controls the operation of the
reference, as shown in Register 22-1. The block
diagram is shown in Figure 22-1.
The comparator and reference supply voltage can
come from either V
and V
comparator reference supply voltage is controlled by
the CVRSS bit.
REGISTER 22-1:
© 2006 Microchip Technology Inc.
Note:
REF
COMPARATOR VOLTAGE
REFERENCE MODULE
-, that are multiplexed with RA3 and RA2. The
The comparator voltage reference is only
available
PIC18F458.
bit 7
bit 6
bit 5
bit 4
bit 3-0
DD
CVRCON: COMPARATOR VOLTAGE REFERENCE CONTROL REGISTER
and V
on
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 CV
0 = 0.25 CV
CVRSS: Comparator V
1 = Comparator reference source, CV
0 = Comparator reference source, CV
CVR<3:0>: Comparator V
When CVRR = 1:
CV
When CVRR = 0:
CV
Legend:
R = Readable bit
-n = Value at POR
CVREN
R/W-0
REF
REF
SS
the
REF
REF
REF
REF
, or the external V
= (CVR3:CVR0/24) (CV
= 1/4 (CV
circuit powered on
circuit powered down
voltage level is also output on the RA0/AN0/CV
voltage is disconnected from the RA0/AN0/CV
PIC18F448
RSRC
RSRC
CVROE
R/W-0
to 0.625 CV
to 0.719 CV
RSRC
REF
REF
REF
) + (CVR3:CVR0/32) (CV
REF
R/W-0
CVRR
and
Range Selection bit
REF
REF
Source Selection bit
Output Enable bit
W = Writable bit
‘1’ = Bit is set
+
RSRC
RSRC
Value Selection 0
RSRC
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.
EQUATION 22-1:
EQUATION 22-2:
The settling time of the Comparator Voltage Reference
must be considered when changing the RA0/AN0/
CV
Characteristics”).
REF
If CVRR = 0:
CV
where:
RSRC
RSRC
= (V
= V
REF
If CVRR = 1:
CV
where:
DD
output (see Table 27-4 in Section 27.2 “DC
CVRSS = 1, CV
CVRSS = 0, CV
REF
/24 step size
/32 step size
Configuring the Comparator
Voltage Reference
REF
CVRSS = 1, CV
CVRSS = 0, CV
= (CV
R/W-0
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
CVR3
– V
CVR3:CVR0
RSRC
+) – (V
= (CVR<3:0>/24) x CV
SS
RSRC
)
REF
REF
REF
x 1/4) + (CVR<3:0>/32) x CV
R/W-0
CVR2
pin
-)
RSRC
RSRC
pin
RSRC
RSRC
PIC18FXX8
15 bits
= (V
= AV
= (V
= AV
REF
x = Bit is unknown
DD
R/W-0
CVR1
REF
DD
RSRC
+) – (V
DS41159E-page 255
– AV
+) – (V
– AV
SS
REF
SS
REF
-)
R/W-0
CVR0
RSRC
-)
bit 0