User Guide

MPLAB

PICkit™ 4 User’s Guide

DS50002751C-page 20  2018 Microchip Technology Inc.

A simplified diagram of some of the internal interface circuitry of the MPLAB PICkit 4

In-Circuit Debugger is shown.

FIGURE 2-8: PROPER CONNECTIONS FOR PROGRAMMING

For programming, no clock is needed on the target device, but power must be supplied.

When programming, the debugger puts programming levels on V

PP/MCLR, sends

clock pulses on PGC and serial data via PGD. To verify that the part has been

programmed correctly, clocks are sent to PGC and data is read back from PGD. This

sequence confirms the debugger and device are communicating correctly.

2.5 REQUIREMENTS FOR DEBUGGING

To debug (set breakpoints, see registers, etc.) with the MPLAB PICkit 4 In-Circuit

Debugger system, there are critical elements that must be working correctly:

• The debugger must be connected to a computer. It must be powered by the

computer via the USB cable and it must be communicating with the MPLAB X IDE

software via the Micro-B USB cable. See Section 3.3 “Debug Tutorial” for

details.

• The debugger must be connected as shown in Figure 2-8 to the Vpp, PGC and

PGD pins of the target device with the modular interface cable (or equivalent).

• The target device must have power and a functional, running oscillator. If the

target device does not run, for any reason, the MPLAB PICkit 4 In-Circuit

Debugger cannot debug.

• The target device must have its configuration words programmed correctly. These

are set using the MPLAB X IDE.

- 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.

- For some devices with more than one PGC/PGD pair, the correct pair needs

to be selected in the device’s configuration word settings. This only refers to

debugging, since programming will work through any PGC/PGD pair.

When the conditions listed above are met, you may proceed to the following:

• Sequence of Operations Leading to Debugging

• Debugging Details

+5V

Programming

VPP/MCLR

PGC

PGD

Internal Circuits

VSS

VDD

Voltage