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JTAG CLK and XCLKIN pin

Other Parts Discussed in Thread: TMS320F28033

Hello everyone,

I am designing a board with the TMS320F28033. I will need to program this with JTAG, connect an external oscillator through XCLKIN and also I need the SPI interface so I need the SPISTEA pin.

In the 64 pin chip, XCLKIN and TCK are shared, and XCLKIN and SPISTEA are shared.

I found this similar question:

https://e2e.ti.com/support/microcontrollers/c2000/f/171/t/244150

The response says I can use a MUX to disable the XCLKIN when I connect the JTAG. But my question is if the JTAG is being used for a debug (reading registers) when the code is running, where does the clock come from? Will I have to use the onboard oscillator? In that case, can the onboard oscillator achieve max speed of operation? Is it completely impossible to not share the JTAG TCK and XCLKIN clocks? Using only a crystal is not possible, we need an external oscillator, so using X1 and X2 for connecting a crystal is not a choice.

Thanks in advance.