User manual

Operation
 2013 Microchip Technology Inc. DS52116A-page 25
2.7 REQUIREMENTS FOR DEBUGGING
To debug (set breakpoints, see registers, etc.) with the PICkit 3 In-Circuit
Debugger/Programmer system, there are critical elements that must be working
correctly:
• The debugger must be connected to a PC. It must be powered by the PC via the
USB cable, and it must be communicating with the MPLAB X IDE software via the
USB cable. See Chapter 3. “Debugger Usage” for details.
• The debugger must be connected as shown in Figure 2-6 to the V
PP, PGC and
PGD pins of the target device with the modular interface cable (or equivalent).
V
SS and VDD are also required to be connected between the debugger and target
device.
• The target device must have power and a functional, running oscillator. If the
target device does not run, for any reason, the PICkit 3 In-Circuit
Debugger/Programmer cannot debug.
• The target device must have its Configuration words programmed correctly:
- The oscillator Configuration bits should correspond to RC, XT, etc., depending
upon the target design.
- For some devices, the Watchdog Timer is enabled by default and needs to be
disabled.
- The target device must not have code protection enabled.
- The target device must not have table read protection enabled.
• PGM (LVP) should be disabled.
When the conditions listed above are met, you may proceed to the following:
• Sequence of Operations Leading to Debugging
• Debugging Details
2.7.1 Sequence of Operations Leading to Debugging
Given that the Requirements for Debugging are met, these actions can be performed
when the PICkit 3 In-Circuit Debugger/Programmer is set as the current tool from the
MPLAB X IDE menu (Edit>Project Properties, Advanced, MPLAB Environment
):
• When Debug>Debug Project
is selected, the application code is programmed into
the device’s memory via the ICSP protocol as described at the beginning of this
section.
• A small “debug executive” program is loaded into the high area of program
memory on the target device. Since the debug executive must reside in program
memory, the application program must not use this reserved space. Some devices
have special memory areas dedicated to the debug executive. Check your device
data sheet for details.
• Special “in-circuit debug” registers in the target device are enabled by MPLAB X
IDE. These allow the debug executive to be activated by the debugger. For more
information on the device’s reserved resources, see Section 2.9 “Resources
Used by the Debugger”.
• The target device is run in Debug mode.