Datasheet

PICkit™ 3 Debug Express Lessons

3.6 LESSON 6: USING PICkit 3 DEBUG EXPRESS

This lesson covers using the PICkit 3 as an In-Circuit-Debugger (ICD). It uses the same

MPLAB IDE workspace and project as Lesson 5. Set T0CON assignment back to the

“no prescale” statement if it was changed in the last lesson.

3.6.1 Resources Reserved by the PICkit 3 Debug Express

The PICkit 3 Debug Express uses some on-chip resources to enable debugging. The

resources are not available to the user application code.

3.6.1.1 GENERAL RESOURCES

•MCLR

pin reserved for debugging; this pin cannot be used as digital I/O while

debugging.

• The PGD and PGC port pins are reserved for programming and in-circuit debug-

ging. Therefore, other functions multiplexed on these pins will not be available

during debug.

• One stack level is used by the debugger and not available.

3.6.1.2 PROGRAM AND DATA MEMORY RESOURCES

The PICkit™ 3 Debug Express uses program memory and file register locations in the

target device during debugging. These locations are not available for use by user code.

In the MPLAB IDE, registers marked with an “R” in register displays represent reserved

registers, as shown in Figure 3-26.

FIGURE 3-26: RESERVED ICD FILE REGISTER LOCATIONS IN THE PIC18F45K20

Key Concepts

- An In-Circuit-Debugger like PICkit 3 uses some on-chip resources to enable

debugging. These reserved file registers and program memory locations are

marked ‘R’ in the MPLAB IDE views, and are not available for use by the

user application.

- Debugging also reserves one level of the hardware return address stack and

two I/O pins.

- Debugging allows the program to be run, halted, stepped-through statement

by statement, and for breakpoints to be set on program statements.

- The number of available breakpoints depends on the PIC microcontroller

being used.

Note: This lesson uses the project and source code from Lesson 5: Using Timer0.