Hardware
2.4
Measure MSP430 Current Draw
To measure the current draw of the MSP430FR6989 using a multi-meter, use the 3V3 jumper on the
jumper isolation block. The current measured includes the target device and any current drawn through
the BoosterPack headers.
To measure ultra-low power, follow these steps:
1. Remove the 3V3 jumper in the isolation block, and attach an ammeter across this jumper.
2. Consider the effect that the backchannel UART and any circuitry attached to the MSP430FR6989 may
have on current draw. Consider disconnecting these at the isolation jumper block, or at least consider
their current sinking and sourcing capability in the final measurement.
3. Make sure there are no floating inputs/outputs (I/Os). These cause unnecessary extra current draw.
Every I/O should either be driven out or, if it is an input, should be pulled or driven to a high or low
level.
4. Begin target execution.
5. Measure the current. Keep in mind that if the current levels are fluctuating, it may be difficult to get a
stable measurement. It is easier to measure quiescent states.
Alternatively, Ener+ technology can be used to measure the same current, and see energy
profiles through integrated GUI in CCS and IAR. EnergyTrace allows you to compare various current
profiles and better optimize your energy performance!
2.5
Clocking
The MSP-EXP430FR6989 provides an external clock in addition to the internal clocks in the device.
•
Y1: 32-kHz MicroCrystal crystal (MS3V)
The 32-kHz crystal allows for lower LPM3 sleep currents than do the other low-frequency clock sources.
Therefore, the presence of the crystal allows the full range of low-power modes to be used.
The internal clocks in the device default to the following configuration:
•
MCLK: DCO 1 MHz
•
SMCLK: DCO 1 MHz
•
ACLK: REFO 32.768 kHz
For more information about configuring internal clocks and using the external oscillators, see the
MSP430FR69xx Family User's Guide
2.6
Using the eZ-FET Emulator with a Different Target
The eZ-FET emulator on the LaunchPad can interface to most MSP430 derivative devices, not just the on-
board MSP430FR6989 target device.
To do this, disconnect every jumper in the isolation jumper block. This is necessary, because the emulator
cannot connect to more than one target at a time over the Spy-Bi-Wire (SBW) connection.
Next, make sure the target board has proper connections for SBW. Note that to be compatible with SBW,
the capacitor on RST/SBWTDIO cannot be greater than 2.2 nF. The documentation for designing MSP430
JTAG interface circuitry is the
MSP430 Hardware Tools User's Guide
Finally, wire together these signals from the emulator side of the isolation jumper block to the target
hardware:
•
5 V (if 5 V is needed)
•
3.3 V
•
GND
•
SBWTDIO
•
SBWTCK
•
TXD (if the UART backchannel is to be used)
•
RXD (if the UART backchannel is to be used)
15
SLAU627A – May 2015 – Revised July 2015
MSP430FR6989 LaunchPad™ Development Kit (MSP
‑
EXP430FR6989)
Copyright © 2015, Texas Instruments Incorporated
