6
Quick Start Guide
TWR-K20D72M Jumper Options
The following is a list of all the jumper options. The default installed jumper
settings are shown in white text within the red boxes.
Jumper
Option
Setting
Description
J6
MCU power connection
ON
Connect on-board 3.3V or 1.8V supply to MCU
OFF
Isolate MCU from power (connect an ammeter to measure current)
J13
VBAT power selection
1-2
Connect VBAT to on-board 3.3V or 1.8V supply
2-3
Connect VBAT to the higher voltage between on-board supply or
coin cell supply
J18
3.3V VOUT selection
ON
Connect USB 3.3V regulator output to MCU_PWR
OFF
Disconnect USB 3.3V regulator output to MCU_PWR
J10
JTAG board power
selection
ON
Connect on-board 5V supply to JTAG port (supports powering
board from JTAG pod supporting 5V supply output)
OFF
Disconnect on-board 5V supply to JTAG port
J15
OSJTAG bootloader
selection
ON
OSJTAG bootloader mode (OSJTAG firmware reprogramming)
OFF
Debugger mode
J16
VREG IN selection
1-2
Regulator powered by OSJTAG 5V output
5-6
VBUS signal on Micro-USB connector J19 connects to VREGIN to
allow stand-alone USB operation
6-8
VBUS signal from elevator connector connects to VREGIN to allow
USB operation with complete tower kit
J17
Board power selection
1-2
K20 USB regulator 3.3V output powers VBRD (MCU_PWR)
3-5
3.3V from on-board regulator powers VBRD (MCU_PWR)
5-7
1.8V from on-board regulator powers VBRD (MCU_PWR)
