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Query regarding TMP 121 or TMP 123 data format

bhanu prakash yakkaluri
Prodigy 45 points
Other Parts Discussed in Thread: TMP121

Hi All,

As per specification TMP121 SBOS273C − JUNE 2003 − REVISED FEBRUARY 2005

the data format for temperature is given in table 2

the last three bits are 000 but from the figure 3 they given the D2 bit as 1

which one we need to consider as a standard data format

for suppose if the last three LSB bits are not zero shall we consider the 16 bit data as a error temperature value

Please Reply as soon as possible

Best Regards,

Bhanu

Temp.pdf
  • 0
    TI__Mastermind 25180 points

    Bhanu,

    You are correct that the datasheet is contradicting itself in this regard and we will address this. Thank you for you pointing this out.

    I have tested the TMP121. Bit D2 is 0 as in Table 2. Please see the oscilloscope capture below.

    Math used:

    1) BIN: 0000 1100 0010 1011     DEC: 3115

    2) Shift  value by 3.                     (DEC) / (23) =  389.375

    3) Multiply by resolution               Temperature = 389.375 * 0.0625oC = 24.3359oC

  • 0 in reply to Chris Featherstone
    Prodigy 45 points

    Hi Chris,

    Thanks for your quick reply.

    Best Regards,

    Bhanu

  • 0 in reply to Chris Featherstone
    Prodigy 45 points

    Hi Chris,

    My job is to verify the Master SPI interface, where TMP121 is a slave SPI,

    so i need to develop a TMP121 BFM to check the master functionality

    my query is

    for suppose, if the last 3 LSB bits are not equal to 011, does the master consider the temperature  is invalid or valid?

    eg: if SPI slave output (TMP121) is 0000 1100 0010 1111, what will be the master response whether it discard the last three bits and calculate the  temperature or it will discard the temperature

    Please reply As Soon As Possible

    Best Regards,

    Bhanu

  • 0 in reply to bhanu prakash yakkaluri
    TI__Mastermind 25180 points

    Bhanu,

    I am currently looking into the functionality of this confirmation bit. The last two bits are high impedance meaning that they can be 0 or 1. The last 2 bits should never be used in the determining the temperature or if there was an error. The confirmation bit will provide useful information. I will get back to you shortly on this.  

  • 0 in reply to bhanu prakash yakkaluri
    TI__Mastermind 25180 points

    Bhanu,

    I have discussed this with the design team. Bit D2 is hard coded to be Zero '0'. It has no meaning and will never be 1. You can ignore this bit and shift the read by 3 bits as shown above to gather the temperature data. Sorry for the confusion and we will work toward clarifying our datasheet. We appreciate your help pointing out these items. 

  • 0 in reply to Chris Featherstone
    Prodigy 45 points

    Thanks Chris,

    A Verification engineer mindset will be destructive creativity and negative thinking towards RTL, that's why i raised all  these queries.

    Once again thanks Chris for you & your team support.

    Best Regard's

    Bhanu