Microchip Technology DV164136 Ficha De Dados
© 2008 Microchip Technology Inc.
DS39646C-page 291
PIC18F8722 FAMILY
24.0
HIGH/LOW-VOLTAGE DETECT
(HLVD)
(HLVD)
The PIC18F8722 family of devices have a
High/Low-Voltage Detect module (HLVD). This is a pro-
grammable circuit that allows the user to specify both a
device voltage trip point and the direction of change from
that point. If the device experiences an excursion past
the trip point in that direction, an interrupt flag is set. If the
interrupt is enabled, the program execution will branch to
the interrupt vector address and the software can then
respond to the interrupt.
High/Low-Voltage Detect module (HLVD). This is a pro-
grammable circuit that allows the user to specify both a
device voltage trip point and the direction of change from
that point. If the device experiences an excursion past
the trip point in that direction, an interrupt flag is set. If the
interrupt is enabled, the program execution will branch to
the interrupt vector address and the software can then
respond to the interrupt.
The High/Low-Voltage Detect Control register
(Register 24-1) completely controls the operation of the
HLVD module. This allows the circuitry to be “turned
off” by the user under software control, which
minimizes the current consumption for the device.
(Register 24-1) completely controls the operation of the
HLVD module. This allows the circuitry to be “turned
off” by the user under software control, which
minimizes the current consumption for the device.
The block diagram for the HLVD module is shown in
Figure 24-1.
Figure 24-1.
REGISTER 24-1:
HLVDCON: HIGH/LOW-VOLTAGE DETECT CONTROL REGISTER
R/W-0
U-0
R-0
R/W-0
R/W-0
R/W-1
R/W-0
R/W-1
VDIRMAG
—
IRVST
HLVDEN
HLVDL3
HLVDL2
HLVDL1
HLVDL0
bit 7
bit 0
Legend:
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
-n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
x = Bit is unknown
bit 7
VDIRMAG: Voltage Direction Magnitude Select bit
1
= Event occurs when voltage equals or exceeds trip point (HLVDL<3:0>)
0
= Event occurs when voltage equals or falls below trip point (HLVDL<3:0>)
bit 6
Unimplemented: Read as ‘0’
bit 5
IRVST: Internal Reference Voltage Stable Flag bit
1
= Indicates that the voltage detect logic will generate the interrupt flag at the specified voltage range
0
= Indicates that the voltage detect logic will not generate the interrupt flag at the specified voltage
range and the HLVD interrupt should not be enabled
bit 4
HLVDEN: High/Low-Voltage Detect Power Enable bit
1
= HLVD enabled
0
= HLVD disabled
bit 3-0
HLVDL<3:0>: Voltage Detection Limit bits
(1)
1111
= External analog input is used (input comes from the HLVDIN pin)
1110
= Maximum setting
.
.
.
0000
= Minimum setting
Note 1:
See Table 28-4 for specifications.