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User Guide

DS-50003529B - 45

Figure 4-6. MPLAB ICD 5 Ready to Begin Debugging - PIC MCU

To nd out whether an application program will run correctly, a breakpoint is typically set early in the

program code. When a breakpoint is set from the user interface of MPLAB X IDE, the address of the

breakpoint is stored in the special internal debug registers of the target device. If using ICSP only,

commands on PGC and PGD communicate directly to these registers to set the breakpoint address.

Next, the Debug > Debug Main Project function is usually selected in MPLAB X IDE. The debugger

instructs the debug executive to run the target application. The target starts from the Reset vector

and executes until the Program Counter reaches the breakpoint address that was stored previously

in the internal debug registers.

After the instruction at the breakpoint address is executed, the in-circuit debug mechanism of the

target device “res” and transfers the device’s program counter to the debug executive (like an

interrupt) and the user’s application is eectively halted. The debugger communicates with the

debug executive via PGC and PGD, gets the breakpoint status information, and sends it back to

MPLAB X IDE. MPLAB X IDE then sends a series of queries to the debugger to get information about

the target device, i.e., le register contents and the state of the CPU. These queries are performed by

the debug executive.

The debug executive runs like an application in program memory or special test memory. It uses

some locations on the stack for its temporary variables. If the device does not run, for whatever

reason (no oscillator, faulty power supply connection, shorts on the target board, etc.), then the

debug executive cannot communicate to the MPLAB ICD 5, and MPLAB X IDE will issue an error

message.

Another way to halt the target is to select Debug > Pause. This toggles the PGC and PGD lines

so that the in-circuit debug mechanism of the target device switches the Program Counter from

the user’s code in program memory to the debug executive. The target application program is

eectively halted, and MPLAB X IDE uses the debugger communications with the debug executive to

interrogate the state of the target device.

4.4.2.4 Requirements for Debugging

To debug (set breakpoints, see registers, etc.) with the MPLAB ICD 5 In-Circuit Debugger system,

there are critical elements that must be working correctly:

• The debugger must be powered, must be connected to a computer, and must be communicating

with the MPLAB X IDE software.

Microchip Technology MPLAB ICD 5 User Manual

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