Microchip Technology MPLAB ICD 4 User Manual

MPLAB
®
ICD 4 User’s Guide
DS50002596A-page 24  2017 Microchip Technology Inc.
2.5.2 Debugging Details
Figure 2-6 illustrates the MPLAB ICD 4 In-Circuit Debugger system when it is ready to
begin debugging.
FIGURE 2-6: MPLAB
®
ICD 4 IN-CIRCUIT DEBUGGER READY TO BEGIN
DEBUGGING
To find 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. 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 tells the debug executive to run. 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 “fires” and transfers the device’s program counter to
the debug executive (like an interrupt) and the user’s application is effectively 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., file 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. 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 4
In-Circuit Debugger, and MPLAB X IDE will issue an error message.
Program
Memory
File
Registers
Internal
Debug
Registers
V PP /MCLR
PGC
PGD
1
5
4
Executive
Debug
Area Used
Tar g e t
be
Running
must
for Debug
Executive
to Function
Area
V DD
Hardware
Stack Shared
by Debug
by Debug
Reserved
for Debug
Executive
MPLAB ICD 4
In-Circuit Debugger
Executive
Executive

Microchip Technology MPLAB ICD 4 Specifications

General

Brand	Microchip Technology
Model	MPLAB ICD 4
Category	Computer Accessories
Language	English