Theory of Operation
©
2009 Microchip Technology Inc.
DS51795A-page 19
2.4.5
Circuits That Will Prevent the Debugger From Functioning
Figure 2-5 shows the active debugger lines with some components that will prevent the
PICkit 3 debugger system from functioning.
FIGURE 2-5:
IMPROPER CIRCUIT COMPONENTS
Specifically, 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
Ω
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 debug communications.
• Do not use capacitors on MCLR – they will prevent fast transitions of V
PP
. A
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.
2.5
DEBUGGING
There are two steps to using the PICkit 3 programmer/debugger system as a debugger.
The first requires that an application be programmed into the target device (usually with
the PICkit 3 itself). The second uses the internal in-circuit debug hardware of the target
Flash device to run and test the application program. These two steps are directly
related to the MPLAB IDE operations:
1.
Program the code into the target and activate special debug functions (see the
next section for details).
2.
Use the debugger to set breakpoints and run.
If the target device cannot be programmed correctly, the PICkit 3
programmer/debugger will not be able to debug.
Figure 2-6 shows the basic interconnections required for programming. Note that this
is the same as Figure 2-4, but for the sake of clarity, the V
DD
and V
SS
lines from the
debugger are not shown.
No!
No!
No!
No!
V
PP
/MCLR
PGC
PGD
1
5
4
Interface
Connector
