PIC18LF4331-ESLASHML datasheet(257/392 Pages) MICROCHIP

257 / 392 page

 2010 Microchip Technology Inc.

DS39616D-page 257

PIC18F2331/2431/4331/4431

22.0

LOW-VOLTAGE DETECT (LVD)

PIC18F2331/2431/4331/4431 devices have a Low-

Voltage Detect module (LVD), a programmable circuit

that enables the user to specify a device voltage trip

point. If the device experiences an excursion below the

trip point, an interrupt flag is set. If the interrupt is

enabled, the program execution will branch to the inter-

rupt vector address and the software can then respond

to the interrupt.

The Low-Voltage Detect Control register (Register 22-1)

completely controls the operation of the LVD 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 LVD module is shown in

Figure 22-1.

The module is enabled by setting the LVDEN bit, but

the circuitry requires some time to stabilize each time

that it is enabled. The IRVST bit is a read-only bit used

to indicate when the circuit is stable. The module can

only generate an interrupt after the circuit is stable and

the IRVST bit is set. The module monitors for drops in

VDD below a predetermined set point.

LVDCON: LOW-VOLTAGE DETECT CONTROL REGISTER

U-0

R-0

R/W-0

R/W-1

R/W-0

R/W-1

—

IRVST

LVDEN

LVDL3(1)

LVDL2(1)

LVDL1(1)

LVDL0(1)

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 7-6

Unimplemented:

Read as ‘0’

bit 5

IRVST:

Internal Reference Voltage Stable Flag bit

= Indicates that the Low-Voltage Detect logic will generate the interrupt flag at the specified voltage

range

= Indicates that the Low-Voltage Detect logic will not generate the interrupt flag at the specified

voltage range and the LVD interrupt should not be enabled

bit 4

LVDEN:

Low-Voltage Detect Power Enable bit

= Enables LVD, powers up LVD circuit

= Disables LVD, powers down LVD circuit

bit 3-0

LVDL<3:0>:

Low-Voltage Detection Limit bits(1)

1111

= External analog input is used (input comes from the LVDIN pin)

1110

= Maximum setting

0010

= Minimum setting

0001

= Reserved

0000

= Reserved

Note 1:

LVDL<3:0> bit modes, which result in a trip point below the valid operating voltage of the device, are not

tested.

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