PIC16F818-ESLASHML datasheet(104/176 Pages) MICROCHIP

104 / 176 page

PIC16F818/819

DS39598E-page 102

 2004 Microchip Technology Inc.

12.18 Low-Voltage ICSP Programming

The LVP bit of the Configuration Word register enables

Low-Voltage ICSP Programming. This mode allows the

microcontroller to be programmed via ICSP using a

VDD source in the operating voltage range. This only

means that VPP does not have to be brought to VIHH but

can instead be left at the normal operating voltage. In

this mode, the RB3/PGM pin is dedicated to the

programming function and ceases to be a general

purpose I/O pin.

If Low-Voltage Programming mode is not used, the LVP

bit can be programmed to a ‘0’ and RB3/PGM becomes

a digital I/O pin. However, the LVP bit may only be

programmed when Programming mode is entered with

VIHH on MCLR. The LVP bit can only be changed when

using high voltage on MCLR.

It should be noted that once the LVP bit is programmed

to ‘0’, only the High-Voltage Programming mode is

available and only this mode can be used to program

the device.

When using Low-Voltage ICSP, the part must be

supplied at 4.5V to 5.5V if a bulk erase will be executed.

This includes reprogramming of the code-protect bits

from an ON state to an OFF state. For all other cases of

Low-Voltage ICSP, the part may be programmed at the

normal operating voltage. This means calibration values,

unique user IDs or user code can be reprogrammed or

added.

The following LVP steps assume the LVP bit is set in the

Configuration Word register.

Apply VDD to the VDD pin.

Drive MCLR low.

Apply VDD to the RB3/PGM pin.

Apply VDD to the MCLR pin.

Follow with the associated programming steps.

Note 1: The High-Voltage Programming mode is

always available, regardless of the state

of the LVP bit, by applying VIHH to the

MCLR pin.

2: While

Low-Voltage

ICSP

mode

(LVP = 1), the RB3 pin can no longer be

used as a general purpose I/O pin.

3: When using Low-Voltage ICSP Program-

ming (LVP) and the pull-ups on PORTB

are enabled, bit 3 in the TRISB register

must be cleared to disable the pull-up on

RB3 and ensure the proper operation of

the device.

4: RB3 should not be allowed to float if LVP

is enabled. An external pull-down device

should be used to default the device to

normal operating mode. If RB3 floats

high, the PIC16F818/819 device will

enter Programming mode.

5: LVP mode is enabled by default on all

devices shipped from Microchip. It can be

disabled by clearing the LVP bit in the

Configuration Word register.

6: Disabling LVP will provide maximum

compatibility

other

PIC16CXXX

devices.

PIC16F818-E/ML Datasheet(PDF) 104 Page - Microchip Technology

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