Developer Help

The Debug Executive

When using an in-circuit debugger to debug your program, some of the chip's resources are reserved for debugging functions. Your code isn't the only thing that gets programmed into the device. A small program called the debug executive is automatically added to your code when you build and program for debugging. It's job is to run commands sent by the PC and to control the debug process. While your program is running, it sits quietly in the background. However, whenever a breakpoint is reached or a command is received from the PC, control over the device is transferred to the debug executive.

Resource Needs

• Exclusive use of two I/O pins
• Shared control of the MCLR pin
• Some file registers (RAM)
• Some program memory locations (Flash)
• One or two hardware (return) stack locations

The debug executive requires a small amount of code space and a few registers in data memory. The exact amount and locations differ from one device to another and are fully described in the debug tool's help file, accessible from the MPLAB X IDE help menu. In addition to on-chip resources, the ICSP™ lines must be dedicated to the debug process. The I/O pins multiplexed with debug clock, data, and PGM (if used) may not be used by your application while debugging.

Example Resource Needs