PIC16F676-ESLASHST datasheet(71/132 Pages) MICROCHIP

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 2010 Microchip Technology Inc.

DS40039F-page 71

PIC16F630/676

9.8

Code Protection

If the code protection bit(s) have not been

programmed, the on-chip program memory can be

read out for verification purposes.

9.9

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 7 bits of the ID locations are used.

9.10

In-Circuit Serial Programming

The PIC16F630/676 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

• programming voltage

This allows customers to manufacture boards with

unprogrammed devices and then program the micro-

controller 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 RA0 and RA1 pins low, while raising the

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

Specification). RA0 becomes the programming data

and RA1 becomes the programming clock. Both RA0

and RA1 are Schmitt Trigger inputs in this mode.

After Reset, to place the device into Programming/Ver-

ify 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 on

whether the command was a load or a read. For

complete details of serial programming, please refer to

the PIC16F630/676 Programming Specification.

A typical In-Circuit Serial Programming connection is

shown in Figure 9-14.

FIGURE 9-14:

TYPICAL IN-CIRCUIT

SERIAL PROGRAMMING

CONNECTION

9.11

In-Circuit Debugger

Since in-circuit debugging requires the loss of clock,

data and MCLR pins, MPLAB® ICD 2 development with

an 14-pin device is not practical. A special 20-pin

PIC16F676-ICD device is used with MPLAB ICD 2 to

provide separate clock, data and MCLR pins and frees

all normally available pins to the user.

This special ICD device is mounted on the top of the

header and its signals are routed to the MPLAB ICD 2

connector. On the bottom of the header is an 14-pin

socket that plugs into the user’s target via the 14-pin

stand-off connector.

When the ICD pin on the PIC16F676-ICD device is

held low, the In-Circuit Debugger functionality is

enabled. This function allows simple debugging

functions when used with MPLAB ICD 2. When the

microcontroller has this feature enabled, some of the

resources are not available for general use. Table 9-10

shows which features are consumed by the

background debugger:

TABLE 9-10:

DEBUGGER RESOURCES

For more information, see 14-Pin MPLAB ICD 2

Header Information Sheet (DS51292) available on

Microchip’s web site (www.microchip.com).

Note:

The entire data EEPROM and Flash

program memory will be erased when the

code protection is turned off. The INTOSC

calibration data is also erased. See

PIC16F630/676 Programming Specifica-

tion for more information.

I/O pins

ICDCLK, ICDDATA

Stack

1 level

Program Memory

Address 0h must be NOP

300h-3FEh

External

Connector

Signals

To Normal

Connections

To Normal

Connections

PIC16F630/676

VDD

VSS

RA3/MCLR/VPP

RA1

RA0

+5V

VPP

CLK

Data I/O

VDD

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