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TLC59291: FC9 bit does nothing: BLANK pin always works as SOUT select 8/16ch

Alberto Farre Gomes
Prodigy 180 points
Part Number: TLC59291

Hello,


I have a setup of 32 TLC59291 chained.


Everything works perfect when controlling outputs ON/OFF and also when playing with FC register, let’s say to play with brightness or to toggle Power Save Mode ON/OFF.

but,

when modifying FC bit 9 to toggle between SOUT 8/16 Select or Blank Mode IT DOES NOTHING:

it always remains in SOUT 8/16 Select Mode whatever I do with FC9, I can see that because all next changes on BLANK pin just toggle between 8/16ch, never acts as Outputs ON/OFF.

Just adding that what I do with FC9 is the same I do with rest of FC bits, and everything works.

Thank you,
Alberto

  • 0
    TI__Genius 11836 points

    Hi Alberto,

        Can you provide some waveforms about your problem?

  • 0 in reply to Charles-Chen
    Prodigy 180 points

    I can provide waveforms if you wish, but keep in mind that I have no problems with any other control bit of FC Word, everything works but bit 9. So it means 2 things:

    1. My procedure seems to be right because I success when acting over the rest of 15 bits of FC word, I can see the results, but for bit 9.
    2. My setup is also right for BLANK pin because I can use it to toggle 8/16ch.

    It seems more like some missed condition at spec in relation with FC9 manipulation. I have already seen some errors, or confusing information, like figure 34 at page 33 that says pin 10 to be BLANK Mode select 1, which does not match with the rest of spec like tables 11 and 12 at page 35.

    Additionally, going back to waveforms, I have to say that I use it asynchronously, just pulling data & control pins up and down, as directed at spec, to insert values into TLC, so it does not help to draw waveforms at oscope. But if it is necessary I can provide it.

    Just as an advanced info, here a pseudo-code of how I use it (in fact, it is more like a waveform matching figure 13 page 20 of spec):

    SIN = 1     //FC15 (1= POWER_SAVE_MODE_ENABLED)

    DELAY_1us

    SCKL = 1

    DELAY_1us

    SCKL = 0

    DELAY_1us

    …

    … (same for FC14, FC13, FC12, FC11, FC10)

    …

    SIN = 1     //FC9 (1= BLANK_TO_ENABLE_MODE)

    DELAY_1us

    SCKL = 1

    DELAY_1us

    SCKL = 0

    DELAY_1us

    …

    … (same for FC8, FC7, FC6, FC5, FC4, FC3, FC2, FC1)

    …

    SIN = 1     //FC0 (BRIGHTNESS LSD)

    DELAY_1us

    SCKL = 1

    DELAY_1us

    SCKL = 0

    DELAY_1us

     

    SCKL = 1

    DELAY_1us

    LAT = 1

    DELAY_1us

    LAT = 0

    DELAY_1us

    SCKL = 0

    DELAY_1us

     

    When using previous procedure, for example, to set brightness it works great.

    When using previous procedure to set FC9 it does nothing: BLANK pin always act as 8/16ch toggle.

    Please let me know if you still need waveforms.

  • 0 in reply to Alberto Farre Gomes
    TI__Genius 11836 points

    Hi Alberto,

        Thanks for your reminding about  confusing information. I will check about this according to your description. FC9(bit 9) should be the bit to configure blank mode and FC10(bit10) is used to configure LED SHORT DETECTION(LSD) THRESHOLD VOLTAGE. 

         Besides, since when the IC is powered on, SOUT mode is selected as default value. Refer to table 7 for detail. If device is already in SOUT mode and the user wants to switch to ENABLE mode. First make sure BLANK pin is high, SOUT is connected with bit15 of common shift register. Then input the new FC data with BIT[9] = 1. The device enters ENABLE mode. Please refer to page28 Blank Mode Selection for details.

         Have you noticed this? Please pay attention to it. And waveforms of BLANK, SIN,SCLK and LAT pins are preferred to figure out the problem.

        

  • 0 in reply to Charles-Chen
    Prodigy 180 points

    Thanks for the advice, but yes, my BLANK pin is always high.

    I am holding BLANK pin high all the time, during previous SOUT Mode because I use it as 16ch output, an also during all process of writing FC data word with BIT[9]=1.

    I am to prepare oscope waveforms as required, but it is going to exactly match figure 13 page 20 of spec (adding BLANK waveform as an always high line).

  • 0 in reply to Alberto Farre Gomes
    TI__Genius 11836 points

    Hi Alberto,

        That's good. Waveforms are helpful to figure out the problem.

  • 0 in reply to Alberto Farre Gomes
    TI__Genius 11836 points

    Hi Alberto,

        I'll close this thread due to inactivity and if you have more questions please reply to it directly and it will open again.

  • 0 in reply to Alberto Farre Gomes
    TI__Genius 11836 points

    Hi Alberto,

         Don't worry. Take your time. Any waveforms updated in the future, the thread will open again and I will reply to you.