3.5 On-board Debugger
The Thunderboard EFM8UB3 contains a microcontroller separate from the EFM8 Universal Bee that provides the user with a on-board
J-Link debugger through the USB micro-B debugging port. This microcontroller is referred to as the "On-board Debugger", and is not
programmable by the user.
In addition to providing code download and debug features, the on-board debugger also presents a virtual COM port for general pur-
pose application serial data transfer.
Figure 3.6 On-Board Debugger Connections on page 8
shows the connections between the target EFM8 device and the on-board
debugger. The figure also shows the presence of the Mini Simplicity Connector, and how this is connected to the same I/O pins. Please
refer to section
4. Debugging
and section
5. Kit Configuration and Upgrades
for more details on debugging.
Mini Simplicity
Connector
RSTb/C2CK
C2D/P2.0
P0.4 [UART1_TX]
P0.5 [UART1_RX]
On-Board
J-Link
Debugger
EXP12_UART_TX
EXP14_UART_RX
EFM8_C2CK
EFM8_C2D
Host
PC
USB
EFM8UB3
Figure 3.6. On-Board Debugger Connections
3.6 EFM8 Reset
The EFM8 MCU can be reset by a few different sources:
• A user pressing the RESET button.
• The on-board debugger pulling the EFM8 RSTb pin low.
• An external debugger pulling the EFM8 RSTb pin low.
In addition to the reset sources mentioned above, the debugger will also issue a reset to the EFM8 when starting up. This means that
removing power to the debugger (unplugging the USB Micro-B cable) will not generate a reset, but plugging the cable back in will cause
a reset as the debugger starts up.
UG308: Thunderboard EFM8UB3 User's Guide
Hardware
silabs.com
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