PIC16F628-20SLASHSS datasheet(112/160 Pages) MICROCHIP

112 / 160 page

PIC16F62X

DS40300B-page 112

Preliminary

14.10

Code Protection

the

code

protection

bit(s)

have

not

been

programmed, the on-chip program memory can be

read out for verification purposes.

14.11

ID Locations

Four memory locations (2000h-2003h) are designated

as ID locations where the user can store checksum or

other code-identification numbers. These locations are

not accessible during normal execution but are

readable and writable during program/verify. Only the

least significant 4 bits of the ID locations are used.

14.12

In-Circuit Serial Programming

The PIC16F62X

microcontrollers can be serially

programmed while in the end application circuit. This is

simply done with two lines for clock and data, and three

other lines for power, ground, and the programming

voltage. This allows customers to manufacture boards

with unprogrammed devices, and then program the

microcontroller just before shipping the product. This

also allows the most recent firmware or a custom

firmware to be programmed.

The device is placed into a program/verify mode by

holding the RB6 and RB7 pins low while raising the

MCLR (VPP) pin from VIL to VIHH (see programming

specification). RB6 becomes the programming clock

and RB7 becomes the programming data. Both RB6

and RB7 are Schmitt Trigger inputs in this mode.

After reset, to place the device into programming/verify

mode, the program counter (PC) is at location 00h. A

6-bit command is then supplied to the device.

Depending on the command, 14-bits of program data

are then supplied to or from the device, depending if the

command was a load or a read. For complete details of

serial programming, please refer to the Programming

Specifications.

A typical in-circuit serial programming connection is

shown in Figure 14-20.

Note:

The entire data EEPROM and FLASH

program memory will be erased when the

code protection is turned off. The INTRC

calibration data is not erased.

FIGURE 14-20: TYPICAL IN-CIRCUIT SERIAL

PROGRAMMING

CONNECTION

14.13

Low Voltage Programming

The LVP bit of the configuration word, enables the low

voltage programming. This mode allows the microcon-

troller to be programmed via ICSP using only a 5V

source. This mode removes the requirement of VIHH to

be placed on the MCLR pin. The LVP bit is normally

erased to ’1’ which enables the low voltage program-

ming. In this mode, the RB4/PGM pin is dedicated to

the programming function and ceases to be a general

purpose I/O pin. The device will enter programming

mode when a ’1’ is placed on the RB4/PGM pin. The

HV programming mode is still available by placing VIHH

on the MCLR pin.

If Low-voltage programming mode is not used, the LVP

bit can be programmed to a ’0’ and RB4/PGM becomes

a digital I/O pin. To program the device, VIHH must be

placed onto MCLR during programming. The LVP bit

may only be programmed when programming is

entered with VIHH on MCLR. The LVP bit cannot be

programmed when programming is entered with

RB4/PGM.

It should be noted, that once the LVP bit is programmed

to 0, only the high voltage programming mode is avail-

able and only high voltage programming mode can be

used to program the device.

Note 1: While in this mode the RB4 pin can no

longer be used as a general purpose I/O

pin.

2: VDD must be 5.0V +10% during erase/pro-

gram operations while in low voltage pro-

gramming mode.

External

Connector

Signals

To Normal

Connections

To Normal

Connections

PIC16F62X

VDD

VSS

RA5/MCLR/THV

RB6

RB7

+5V

VPP

CLK

Data I/O

VDD

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