PIC16F690 datasheet(2/78 Pages) MICROCHIP

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Debug Header Specification

DS51292T-page 2

 2006-2012 Microchip Technology Inc.

WHY DO I NEED A HEADER TO DEBUG?

Some PIC® microcontrollers, particularly low pin count devices (with 20 pins or less),

generally must use a header for debugging. This is done to free up I/O lines for your

application and to make production parts more affordable. Optional headers are also

available for high pin count devices (with 64 pins or higher).

Debugging requires a two-line connection (plus VDD, VSS and VPP) to communicate

with the device. In a high pin count device, losing a few I/O lines is generally not a prob-

lem for most designs. But in a low pin count device, it can be a critical problem. Imagine

having to do an 8-pin design where there are only 5 I/Os, having used up 2 I/Os just for

debugging!

Headers are also used to save you money. In high pin count devices, adding debugging

to the silicon can generally be done at little or no cost since the silicon is already fairly

large. However, low pin count devices are low cost specifically because they use very

little silicon. So, adding debugging circuitry on-board these parts would add significant

cost since it would raise the amount of silicon used by a considerable percentage. The

header places the cost for debugging up front and frees your production parts from the

extra cost of an unused debug module.

Microchip also makes optional debug modules, usually for high pin count devices. The

module is optional because you can still do basic debugging without a header, but if

you use one, you get back I/O lines, and may also gain additional debugging features.

Only certain devices can use an optional header, see the device page on our website

for details.

Microchip lists what header must be ordered to work with your device, if one is required.

Simply consult the device page on our website, or our other ordering guides.

Note that in all cases, devices can be programmed “in circuit” (called ICSP™) with very

few exceptions. Even devices without an internal debug feature can still be pro-

grammed by connecting the programming/debugging tool to the in-circuit programming

lines. These devices simply cannot perform debugging without a header.

FIGURE 1:

PRODUCTION DEVICE VS. HEADER DEVICE (-ICE/-ICD)

ENABLE

ICDMCLR

VDD

ICDCLK

ICDDATA

Vss

ICD

JP1

VDD

To Tool Connector

VDD

Vss

-ICE/ICD Device on Debug Header

Production Device

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