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MSP430F5510: Conditions for the PUR pin to be recognized as HIGH

Conor
Guru 12815 points
Part Number: MSP430F5510
Other Parts Discussed in Thread: TUSB4020BI

Hi,

I have a question about the timing of USB BSL decisions. Currently, TUSB4020BI is connected to the front stage of MSP430.

A pulse of about 2V is input from the TUSB4020BI to the D + for the master and slave handshake. Since D + and PUR are connected via a resistor, about 2.0V is input to PUR as well.

This phenomenon occurs when "battery charging negotiation" of TUSB4020BI is enabled.

Below is a past E2E link that describe this.
https://e2e.ti.com/support/interface-group/interface/f/interface-forum/1043892/tusb4020bi-pulse-width

With this in mind, I have a question about MSP430.

1. Is there any information on the voltage range that PUR recognizes as HIGH? There was a description about GPIO, but is the PUR terminal in the same range?

2. Is there any information on the HIGH duration that PUR recognizes as HIGH?
(It is necessary to continue HIGH for at least 1ms. etc...)

3. When "battery charging negotiation" of TUSB4020BI is enabled, a voltage of about 2.0V is input to PUR. As a result, BSL will occur by mistakenly recognizing that PUR has been pulled up.
Please let me know if there is any way to deal with it other than disabling "battery charging negotiation".

Thanks,

Koki

  • 0
    TI__Mastermind 26850 points

    Hi Koki,

    The PUR pin is used to trigger BSL and it does this with a high signal when the MCU first loads through the bootcode. So to trigger the PUR high it would be the same as those GPIO pins and for timing it would need to be high during the bootcode process AKA device startup.

    Looks like the PUR is getting pulled high after reset, it should be fine if you unplug the device to reset but, if you click the reset button then that could be why PUR is getting triggered. Is your switch bad? or have you tried having the switch off during the reset then switch it back on after startup.

    Regards,

    Luke

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