PIC16C83 datasheet(52/117 Pages) MICROCHIP

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PIC16C8X

DS30081F-page 52

8.9

Code Protection

The code in the program memory and data EEPROM

memory can be protected by programming the code

protect bit (Figure 8-1, Figure 8-2, and Figure 8-3).

8.9.1

ROM DEVICES

There are two protection conﬁguration bits. One for the

program memory, which is speciﬁed as part of the ROM

code submittal. The second for the EEPROM data

memory. When ROM devices complete testing, the

EEPROM data memory code protect conﬁguration bit

will be programmed to the same state as the program

memory code protect conﬁguration bit.

In applications where the device is code protected and

the data EEPROM needs to be programmed before

being placed in the application, the data EEPROM

memory array needs to be erased and then the data

memory code protect disabled. This will allow the

desired data to be programmed into the device. The

sequence to disable the data EEPROM memory

protection is shown in the PIC16C84 Programming

Speciﬁcation (Literature number DS30189D) in Section

3.1.1.

After programming the data EEPROM memory array,

the data EEPROM memory code protect conﬁguration

bit should be programmed as desired.

8.10

ID Locations

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

as ID locations to store checksum or other code

identiﬁcation

numbers. These

locations

are

not

accessible during normal execution but are readable

and writable only during program/verify. Only the

4 least signiﬁcant bits of ID location are usable.

For ROM devices, these values are submitted along

with the ROM code.

8.11

In-Circuit Serial Programming

PIC16C8X

microcontrollers

can

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. Customers can manufacture boards with

unprogrammed

devices,

and

then

program

the

microcontroller just before shipping the product,

allowing the most recent ﬁrmware or 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 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) points to location 00h.

A 6-bit command is then supplied to the device, 14-bits

of program data is then supplied to or from the device,

using load or read-type instructions. For complete

details of serial programming, please refer to the

PIC16CXX Programming Speciﬁcations (Literature

#DS30189).

FIGURE 8-20: TYPICAL IN-SYSTEM SERIAL

PROGRAMMING

CONNECTION

For ROM devices, both the program memory and Data

EEPROM memory may be read, but only the Data

EEPROM memory may be programmed.

External

Connector

Signals

To Normal

Connections

To Normal

Connections

PIC16CXX

VDD

VSS

MCLR

RB6

RB7

+5V

VPP

CLK

Data I/O

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