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TMS570LS1114: ViH specification of PORRST pin

Juergen Mayr
Prodigy 80 points
Part Number: TMS570LS1114
Other Parts Discussed in Thread: TMS570LS0332

I want to know for a calucation the ViH input specification of the TMS570LS1114/TMS570LS0332 PORRST power on reset pin. In the TMS570LS1114 datasheet I found in the general input specifications no hint to consider the PORRST pin different. The TMS570LS0332 datasheet has a dedicated hint. If you look to the PORRST Requirement chapter, I only found a specification for ViL(PORRST) but not for ViH(PORRST).

Therefore the question concerning the ViH(PORRST) min. = ? voltage specification?

Is the PORRST pin ViH value the same like the general input ViH specification for all other I/O pins?

  • 0
    TI__Guru 59540 points

    Hello Juergen,

    TI does not specify VIH for nPORRST as it is very nearly impossible since when the threshold is passed, reset is asserted and the CPU no longer functions. Instead, TI specifies a minimum voltage at which nPORRST must be asserted. This voltage is given in Table 6-4 of the datasheet regarding electrical requirements for nPORRST. Specifically it shows:

  • 0 in reply to Chuck Davenport
    Prodigy 80 points
    Hello Chuck,

    I think nPORRST is low active and I want to know the min. ViH level on the nPORRST pin, when the power-on reset is deasserted. I want to know it, when the TMS570 microcontroller is fully powered. So this should be possible to specifiy, because the controller starts to work after the deassertion of nPORRST.
    Is the VIH(PORRST) also specified with min. 2V up to max. VCCIO+0.3V like the general inputs are specified?
    Or does it have an other specification?

    Thanks and Regards

    Juergen
  • 0 in reply to Juergen Mayr
    TI__Guru 59540 points

    Hello Juergen,

    VIH for nPORRST is not specified nor was it characterized. Generally speaking, one would expect the VIH to be similar to other GPIO, but we cannot guarantee this given the lack of characterization.

    Juergen Mayr said:
    Is the VIH(PORRST) also specified with min. 2V up to max. VCCIO+0.3V like the general inputs are specified?
    Or does it have an other specification?

    As VIH is not characterized, the answer to this question is no.

  • 0 in reply to Juergen Mayr
    TI__Guru 59540 points
    Hello Juergen,

    I have had some additional discussions with my colleague on this topic. Vih and Vil for nPORRST were characterized. Vih is the same as for the other pins (the note 2 should only apply to Vil). Vil for nPORRST is described in section 6.3 on nPORRST electrical and timing requirements.

    In regard to your questiion:
    "Is the VIH(PORRST) also specified with min. 2V up to max. VCCIO+0.3V like the general inputs are specified?"

    The test conditions are provided in the Electrical Specifications Table where VIH is provided.