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PCA9539: Data transition timing

Yuto Sakai
Mastermind 6100 points

Part Number: PCA9539
Other Parts Discussed in Thread: PCF8575

Hi,

What is the data transition timing?
Our customer want to switch 16-bit at the same time. Is it possible?
If we read the data sheet, we can understand that it switches each 8 bits.

Best regards,
Yuto Sakai

  • 0
    TI__Guru* 78111 points

    Hello Yuto-san,

    "Our customer want to switch 16-bit at the same time. Is it possible?"

    Unfortunately not.

    "If we read the data sheet, we can understand that it switches each 8 bits."

    Thats correct. The device will update its ports (meaning 8 bits) at a time and during the rising ACK pulse of a write. This is shown in figure 15 under the write mode where you can see tpv shown.

    May I ask what application you are working on in which you need all 16 bits to change at the exact same time?

    -Bobby

  • 0 in reply to BOBBY
    Mastermind 6100 points

    Hi Bobb-san,

    I'm confirming the application.

    I'm sorry, there was a lack of explanation.
    Do the output statuses of P00 to 07 and P10 to 17 switch at the same time?

    Best regards,
    Yuto Sakai

  • 0 in reply to Yuto Sakai
    TI__Guru 62920 points

    Sakai-san,

    When the output port register for an 8-bit bank is modified, the corresponding P-port outputs will all switch to the new value within 200 ns of the ACK bit of the write command.  So, P00 to P07 would all change together after a write to Output Port 0, while P10 to P17 would all change together after a write to Output Port 1.

    Regards,
    Max

    Edit: corrected typo - thanks Bobby for pointing that out.

  • 0 in reply to Miguel Robertson
    Mastermind 6100 points

    Hi Max-san,

    Thank you for your reply.
    Is "P01" wrong? Is it P00 correctly? Or is it P10?
    If "P10" is correct, isn't the output status of P00 to 07 and P10 to 17 switched at the same time?
    Even if the write timings are different, it is expected that the output statuses switch at the same time.

    Best regards,
    Yuto Sakai

  • 0 in reply to Yuto Sakai
    TI__Guru* 78111 points

    Hello Yuto-san,

    "Is "P01" wrong? Is it P00 correctly? Or is it P10?"

    There is a typo in Max's reply: '......while P01 to P17....' P01 is meant to be P10

    "Even if the write timings are different, it is expected that the output statuses switch at the same time."

    No, our device will change P00-P07 (8 bits all at a time) and P10-P17 (8 bits all at a time). But not all 16 bits all at the same time.

    -Bobby

  • 0 in reply to BOBBY
    Mastermind 6100 points

    Hi Bobby-san,

    Thank you foryour reply.
    Could you tell me which devices can switch 16bit at the same time?

    Best regards,
    Yuto Sakai

  • 0 in reply to Yuto Sakai
    TI__Guru* 78111 points

    Hey Yuto-san,

    We don't have any I2C devices which can switch more than 8 bits at a time. This might be something you have to find a SPI protocol device (I'm not aware of one from TI though).

    -Bobby

  • 0 in reply to BOBBY
    TI__Guru* 78111 points

    Yuto-san,

    Disregard my earlier post, a collegue of mine saw this post and reminded me of the PCF8575 device. This device doesn't update it's P-Ports (16 bits) until it receives a write of 16 bits. So the PCF8575 should be able to provide 16 bits changing at once for you.

    -Bobby