Microchip Technology AC244049 Data Sheet
Processor Extension Pak and Header Specification
DS51292U-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).
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 V
DD
, V
SS
and V
PP
) 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!
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.
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.
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.
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.
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
V
DD
ICDCLK
ICDDATA
Vss
ICD
NC
1
2
3
4
5
6
7
20
19
18
17
16
15
14
JP1
2
1
3
V
DD
To Tool Connector
8
9
10
11
12
13
V
DD
Vss
1
2
3
4
5
6
7
14
13
12
11
10
9
8
-ICE/ICD Device on Debug Header
Production Device