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MPC5777M LBIST on mixed 3V3/5V board

Question asked by jschloss on Feb 16, 2018

Hi,

 

We are developing a module using the MPC5777M (512 pin variant), and are allowing for configurable VDD_HV_IO_MAIN, so that a switch on the board can change the default power level to 3V3 or 5, and the MCU can override it to 3V3 or 5V. We think that this will give us flexibility to boot at 3V3 (after programming dcf records at 5V once) while still letting us go high-z and switch to 5V mode to self-program flash.

 

I noticed that the datasheet states that LBIST is only guaranteed at 4V5 on VDD_HV_PMC, which for us is VDD_HV_IO_MAIN. Do all of the LBIST tests require 5V, or only the LBIST tests that use flash?

 

Is it possible for us to keep an output pin set while running online LBIST/MBIST? We would potentially need to keep the io pin asserted to keep the power supply set to 5V.

 

Does the LBIST/MBIST affect any other pin states? Does it force the pins to pull up like reset does?

 

Thanks,

 

Jacob Schloss

R&D Engineer

 

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