PIC16F684 datasheet(116/192 Pages) MICROCHIP

116 / 192 page

PIC16F684

DS41202F-page 114

12.10 In-Circuit Serial Programming

The PIC16F684 microcontrollers can be serially

programmed while in the end application circuit. This is

simply done with five connections for:

•clock

•data

• 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)

from

VIL

VIHH.

See

the

“PIC12F6XX/16F6XX

Memory

Programming

Specification” (DS41204) for more information. RA0

becomes the programming data and RA1 becomes the

programming clock. Both RA0 and RA1 are Schmitt

Trigger inputs in Program/Verify mode.

A typical In-Circuit Serial Programming connection is

shown in Figure 12-11.

FIGURE 12-11:

TYPICAL IN-CIRCUIT

SERIAL PROGRAMMING

CONNECTION

12.11 In-Circuit Debugger

Since in-circuit debugging requires access to three

pins, MPLAB® ICD 2 development with a 14-pin device

is not practical. A special 20-pin PIC16F684 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.

A special debugging adapter allows the ICD device to

be used in place of a PIC16F684 device. The

debugging adapter is the only source of the ICD device.

When the ICD pin on the PIC16F684 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 12-9 shows which

features are consumed by the background debugger.

TABLE 12-9:

DEBUGGER RESOURCES

For more information, see “MPLAB® ICD 2 In-Circuit

Debugger User’s Guide” (DS51331), available on

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

FIGURE 12-12:

20-PIN ICD PINOUT

External

Connector

Signals

To Normal

Connections

To Normal

Connections

PIC16F684

VDD

VSS

MCLR/VPP/RA3

RA1

RA0

+5V

VPP

CLK

Data I/O

* Isolation devices (as required)

Resource

Description

I/O pins

ICDCLK, ICDDATA

Stack

1 level

Program Memory

Address 0h must be NOP

700h-7FFh

20-Pin PDIP

In-Circuit Debug Device

ICDMCLR/VPP

VDD

RA5

RA4

RA3

ICDCLK

ICDDATA

Vss

RA0

ICD

RA1

RA2

RC5

RC4

RC3

RC0

RC1

RC2

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