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Original question:

PCA9546A: Asking for the cascade PCA9546APWR design feasibility

PCA9546A: About cascade connection and address specification

Tsukui Yusuke
Guru 21930 points
Part Number: PCA9546A
Other Parts Discussed in Thread: PCA9538, PCA9515B

Hi,

Let me ask you about the PCA9546A connection method that customers are challenging.
Customer is considering the following connection circuit.

１．Does PCA9546A support the following connection methods?

２．If question 1 is Yes, Could you please tell me how to assign a second PCA9546A address?
　　Customer wants to know the addressing method of PCA9546A(2) and ② in detail.
　　
 

Best regards,
Yusuke

  • 0
    TI__Guru* 75871 points

    Tsukui Yusuke said:

    Part Number: PCA9546A

    Hi,

    Let me ask you about the PCA9546A connection method that customers are challenging.
    Customer is considering the following connection circuit.

    １．Does PCA9546A support the following connection methods?

    [Bobby] Yes, the device does support series implementation with other I2C switches (as long the device address is unique when in series and ch enabled). This includes downstream devices as well (downstream must be unique).

    ２．If question 1 is Yes, Could you please tell me how to assign a second PCA9546A address?

    [Bobby] The downstream switch must have a unique address when the channel is enabled.
    　　Customer wants to know the addressing method of PCA9546A(2) and ② in detail.

    [Bobby] (2) currently has a conflicting address with the PCA9546A(2) so this will not work. Change A2 on PCA9546A to be '1.' I believe this should allow this diagram you showed to work as long as only one channel is enabled at a time.
    　　
     

    Best regards,
    Yusuke

  • 0 in reply to BOBBY
    Guru 21930 points

    Hi Bobby,

    Thank you for your kind support.

    [Bobby] Yes, the device does support series implementation with other I2C switches (as long the device address is unique when in series and ch enabled). This includes downstream devices as well (downstream must be unique).

    Thank you for your check. I understand.
    In that case, how should we implement the method to access PCA9538④?
    About access from CPU to ④, Customer do not know how to specify the address in ④.
    Customer wont to know how to access ④ via PCA9546A and PCA9515B.
    Could you give me your advice?

    [Bobby] (2) currently has a conflicting address with the PCA9546A(2) so this will not work. Change A2 on PCA9546A to be '1.' I believe this should allow this diagram you showed to work as long as only one channel is enabled at a time.

    PCA9546A address is different.
    -PCA9546(1):A0=1,A1=0,A2=0
    -PCA9546(2):A0=0,A1=0,A2=0
    Why did you think you needed an A2 change?
    Do you have a problem with the duplicate addresses of PCA9538② and PCA9538③?

    Best regards,
    Yusuke

  • 0 in reply to Tsukui Yusuke
    TI__Guru* 75871 points

    Tsukui Yusuke said:

    Hi Bobby,

    Thank you for your kind support.

    [Bobby] Yes, the device does support series implementation with other I2C switches (as long the device address is unique when in series and ch enabled). This includes downstream devices as well (downstream must be unique).

    Thank you for your check. I understand.
    In that case, how should we implement the method to access PCA9538④?
    About access from CPU to ④, Customer do not know how to specify the address in ④.
    Customer wont to know how to access ④ via PCA9546A and PCA9515B.
    Could you give me your advice?

    [Bobby]
    Enable  channel 2 of PCA9546A (in your diagram address is 0x71h) by writing 0x04h then issue a stop condition, then you can communicate directly with PCA9538 (4) {address 0x73h}

    [Bobby] (2) currently has a conflicting address with the PCA9546A(2) so this will not work. Change A2 on PCA9546A to be '1.' I believe this should allow this diagram you showed to work as long as only one channel is enabled at a time.

    PCA9546A address is different.
    -PCA9546(1):A0=1,A1=0,A2=0
    -PCA9546(2):A0=0,A1=0,A2=0
    Why did you think you needed an A2 change?
    [Bobby]
    PCA9538's address is 111 00XX; Number(2) therefore has an address of 0x70h in your diagram

    PCA9546A (1) has an address of 111 0XXX; In your diagram, this is 0x70h.... This means (1) and (2) have the same address when (1) enables channel 3.


    Do you have a problem with the duplicate addresses of PCA9538② and PCA9538③?
    [Bobby]
    The address looks unique to me, as long as channel 2 and channel 0 enabled at the same time.

    Best regards,
    Yusuke