Microchip Technology MPLAB ICD 3 User Manual page 19

2.4.5
Figure 2-5
MPLAB ICD 3 In-Circuit Debugger system from functioning.
FIGURE 2-5:
In particular, these guidelines must be followed:
• Do not use pull-ups on PGC/PGD – they will disrupt the voltage levels, since
these lines have 4.7 k pull-down resistors in the debugger.
• Do not use capacitors on PGC/PGD – they will prevent fast transitions on data
and clock lines during programming and debugging communications.
• Do not use capacitors on MCLR – they will prevent fast transitions of V
simple pull-up resistor is generally sufficient.
• Do not use diodes on PGC/PGD – they will prevent bidirectional communication
between the debugger and the target device.
 2012-2014 Microchip Technology Inc.
Circuits That Will Prevent the Debugger From Functioning
shows the active debugger lines with some components that will prevent the
IMPROPER CIRCUIT COMPONENTS
V /MCLR
PP
No!
PGC
PGD
No!
1
No!
No!
5
4
Interface
Connector
Operation
. A
PP
DS50002081B-page 19