User manual

MPLAB
®
X PICkit™ 3 User’s Guide
DS52116A-page 22  2013 Microchip Technology Inc.
2.5.2 Target Connection Circuitry
Figure 2-4 shows the interconnections of the PICkit 3 In-Circuit Debugger/Programmer
to the connector on the target board. The diagram also shows the wiring from the
connector to a device on the target PC board. A pull-up resistor (typically around 10 k)
is recommended to be connected from the V
PP/MCLR line to VDD so that the line may
be strobed low to reset the device.
FIGURE 2-4: STANDARD CONNECTION TARGET CIRCUITRY
2.5.3 Target Powered
In the following descriptions, only three lines are active and relevant to core debugger
operation: pins 1 (V
PP/MCLR), 5 (PGC) and 4 (PGD). Pins 2 (VDD) and 3 (VSS) are
shown on Figure 2-4 for completeness. PICkit 3 has two configurations for powering
the target device: internal debugger and external target power.
The recommended source of power is external and derived from the target application.
In this configuration, target V
DD is sensed by the debugger to allow level translation for
the target low-voltage operation. If the debugger does not sense voltage on its V
DD line
(pin 2 of the interface connector), it will not operate.
2.5.4 Debugger Powered
The internal debugger power is limited to 30 mA. This can be helpful with very small
applications that have the device V
DD separated from the rest of the application circuit
for independent programming. However, is not recommended for general usage
because imposes more current demands from the USB power system derived from the
PC.
Not all devices have the AV
DD and AVSS lines, but if they are present on the target
device, all must be connected to the appropriate levels in order for the debugger to
operate. They cannot be left floating.
Also, devices with a V
CAP line (PIC18FXXJ MCUs, for example) should be connected
to the appropriate capacitor or level.
VDD
VPP/MCLR
PGC
PGD
V
SS
AVDD
AVSS
2
1
5
4
3
4.7K-10K
Interface
Connector
Application
PC Board
Device
Note: The interconnection is very simple. Any problems that occur are often
caused by other connections or components on these critical lines that
interfere with the operation of the PICkit 3 In-Circuit
Debugger/Programmer.