PIC18F4520ESLASHMLQTP datasheet(245/390 Pages) MICROCHIP

245 / 390 page

 2004 Microchip Technology Inc.

DS39631A-page 243

PIC18F2420/2520/4420/4520

22.0

HIGH/LOW-VOLTAGE

DETECT (HLVD)

PIC18F2420/2520/4420/4520

devices

have

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 22-1) 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 22-1.

HLVDCON REGISTER (HIGH/LOW-VOLTAGE DETECT CONTROL)

R/W-0

U-0

R-0

R/W-0

R/W-1

R/W-0

R/W-1

VDIRMAG

—

IRVST

HLVDEN HLVDL3(1) HLVDL2(1) HLVDL1(1) HLVDL0(1)

bit 7

bit 0

bit 7

VDIRMAG: Voltage Direction Magnitude Select bit

= Event occurs when voltage equals or exceeds trip point (HLVDL3:HLDVL0)

= Event occurs when voltage equals or falls below trip point (HLVDL3:HLVDL0)

bit 6

Unimplemented: Read as ‘0’

bit 5

IRVST: Internal Reference Voltage Stable Flag bit

= Indicates that the voltage detect logic will generate the interrupt flag at the specified voltage

range

= 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

= HLVD enabled

= HLVD disabled

bit 3-0

HLVDL3:HLVDL0: 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 26-4 for specifications.

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

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