User manual

 2011 Microchip Technology Inc. DS41581A-page 27
3.2.15 Programming Interfaces
The PICkit header (J3) can be used by either the PICkit™ 2 or PICkit™ 3 programming
devices. Through use of the PICkit 3 the user is capable of debugging the included
demonstration software or creating and debugging custom software in use with the
8-bit XLP.
3.3 CURRENT MEASUREMENT
An advantage to the XLP 8-bit board is its provisions for in-circuit current measurement.
Using simple techniques and equipment, users can experiment directly with low-power
hardware and software techniques, then directly measure their current consumption
without introducing measurement induced artifacts. This provides a fast method of
directly validating power-saving strategies. To make measurements more useful, the
development board allows for the measurement of microcontroller current draw and
non-microcontroller component current separately.
3.3.1 PIC16LF1947 and PIC18F87K22 Current Measurement
To measure current consumed by the PIC microcontrollers, the VMCU jumper (J15)
can be removed and a current measurement cable connected to its pins. This allows
the user to empirically evaluate the microcontroller’s various low-power features. Since
J15 interrupts the microcontroller’s V
DD path, always be certain to re-install the jumper
when measurements are not being taken. To avoid starving the microcontroller’s cur-
rent supply and causing low-power conditions, it may be necessary to switch the
ammeter to a higher current range during programming and full-power operation. When
the microcontroller is operating in a low-power state, switching to a low range will pro-
duce a more accurate measurement.
3.3.2 Development Board Power Measurement
The VBOARD jumper (J16) allows the user to measure the current consumed by the
various board components. It also permits the user to experiment with low-power tech-
niques on a variety of commonly used components. Current measurements taken at
J16 exclude current consumption from the microcontroller, ICSP™ header and the
USB interface. Therefore, communications with a host PC and emulator/programmer
connections do not need to be accounted for in determining an accurate current mea-
surement, as they are not included in the first place. Since J16 interrupts the V
DD path
to the board’s other components, always be certain to re-install the jumper when mea-
surements are not being taken.
3.3.3 Ammeter Tool Header
The XLP 8-bit board includes a special 7-pin header (J14) for current measurement.
The PIC MCU VMCU and VBOARD jumpers (J15 and J16) ensure continuity of power
when connecting or disconnecting a current measurement device. Microchip provides
an optional XLP Current Measurement Cable (part number AC002023) as a convenient
way of connecting the header to an ammeter.
Note: Since the resistor is placed in series with the PIC MCU V
DD pin, the result-
ing voltage drop may affect power calculations. Ensure calculations are
based on actual V
DD, instead of the supplied board voltage.