PIC12F675T-ESLASHP datasheet(69/136 Pages) MICROCHIP

69 / 136 page

 2010 Microchip Technology Inc.

DS41190G-page 69

PIC12F629/675

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 PIC12F629/675 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

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 GP0 and GP1 pins low, while raising the

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

Specification). GP0 becomes the programming data

and GP1 becomes the programming clock. Both GP0

and GP1 are Schmitt Trigger inputs in this mode.

After Reset, to place the device into Programming/

Verify mode, the 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

Programming Specifications.

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 8-pin device is not practical. A special 14-pin

PIC12F675-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 8-pin

socket that plugs into the user’s target via the 8-pin

stand-off connector.

When the ICD pin on the PIC12F675-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 8-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

PIC12F629/675 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

PIC12F629/675

VDD

VSS

GP3/MCLR/VPP

GP1

GP0

+5V

VPP

CLK

Data I/O

VDD

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