We are designing a circuit with Aurix TC387. The micro controller is powered from 5V ( both VEXT and VFLEX).
We want to connect an ETAS XETK S20.1-B to the micro controller's DAP port for calibration. We saw that the DAP/ JTAG pins belongs to the VEXT domain and therefore 5V in our design. However, ETAS confirmed that the XETK S20.1-B supports only 3.3V DAP. Is there any simple solution without changing the microcontroller power supply to 3.3V?
Can we mitigate this by simply pulling-up the TCK, DAP1/TMS and DAP2 /TDI lines to 3.3V on our board? We are worried that, as there is no way to define the logic levels (TTL/ CMOS) for the TCK and TMS the micro controller will not treat 3.3V at these pins as a HIGH. OR do we need a level shifter?
Will a level shifter be mandatory in such applications? If a level shifter is the only solution, what type( single direction/ bi-direction) is needed for the DAP0, DA1 and DAP 2 pins? can you suggest any specific level-shifters ?
Can anyone please help? Thanks.
DAP is TTL as described in the following document page 77.
The Buffer Type of TCK, DAP1, and DAP2 is FAST as described in the following document. The TTL input low voltage level of the Fast 5V GPIO is 0.8V, as described in page 296 of the following document.
The output of the DAP might be 5V, could you please check the output of TC38x?
If TC38x outputs 5V, please check with tool vendor that the 3.3V tool is able to accept 5V signals.