PIC18F2331/2431/4331/4431
22.5 Operation During Sleep
22.7 Applications
When enabled, the LVD circuitry continues to operate
during Sleep. If the device voltage crosses the trip
point, the LVDIF bit will be set and the device will wake-
up from Sleep. Device execution will continue from the
interrupt vector address if interrupts have been globally
enabled.
Figure 22-3 shows a possible application voltage curve
(typically for batteries). Over time, the device voltage
decreases. When the device voltage equals voltage,
VA, the LVD logic generates an interrupt. This occurs at
time, TA. The application software then has the time,
until the device voltage is no longer in valid operating
range, to perform “housekeeping tasks” and to shut
down the system. Voltage point, VB, is the minimum
valid operating voltage specification. This occurs at
time, TB. The difference, TB – TA, is the total time for
shutdown.
22.6 Effects of a Reset
A device Reset forces all registers to their Reset state.
This forces the LVD module to be turned off.
FIGURE 22-3:
TYPICAL LOW-VOLTAGE DETECT APPLICATION
VA
VB
Legend:
VA = LVD trip point
VB = Minimum valid device
operating voltage
TB
TA
Time
TABLE 22-1: REGISTERS ASSOCIATED WITH LOW-VOLTAGE DETECT MODULE
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
LVDCON
INTCON
IPR2
—
—
IRVST
LVDEN
INT0IE
EEIP
LVDL3
RBIE
—
LVDL2
TMR0IF
LVDIP
LVDIF
LVDL1
INT0IF
—
LVDL0
RBIF
GIE/GIEH PEIE/GIEL TMR0IE
OSCFIP
OSCFIF
OSCFIE
—
—
—
—
—
—
CCP2IP
CCP2IF
CCP2IE
PIR2
EEIF
—
—
PIE2
EEIE
—
LVDIE
—
Legend: — = unimplemented, read as ‘0’. Shaded cells are unused by the LVD module.
2010 Microchip Technology Inc.
DS39616D-page 261
MICROCHIP [ MICROCHIP ]
