TWRKL25Z Tower Module Errata Page 2 of 4
1
ERRATA
This document describes errata on the TWR-KL25Z rev. C board as well as their workarounds.
1.1
External jtag usage
1.1.1
Issue description
The usage of level shifters in the communication between the integrated debugger (OpenSDA) and the target MCU
(KL25) is needed because the OpenSDA debugger runs at 3.3 volts while the KL25 can run at 3.3 or 1.8 volts. One of
the level shifters that is used in the circuit is configured for a fixed direction of communication, which means that
when not in use by the OpenSDA, the pin is kept in a fixed state. This fixed state inhibits external debuggers to work
when the OpenSDA is powered (by connecting the mini USB connector).
The problematic signal is highlighted below.
1.1.2
Workaround
To avoid the OpenSDA keeping this signal fixed so that an external debugger can be used, the OpenSDA needs to be
unpowered. There are two available ways to power the board without powering the OpenSDA:
-
Power through elevators: use the tower elevators and power the board through them.
-
Stand-alone through the micro USB: the TWR-KL25Z includes a micro USB connector that is connected to the
USB port in the KL25 device. The power input from this USB port is connected to the internal KL25 USB
regulator and this regulator output can be routed to power the board by placing to jumpers (J6 and J18) in
