TXS02612: Can I hotswap SDcard by not selecting the port by SEL pin?

Hey Shanu,

The two recommended methods by the SD standard for handling multiple SD devices are as follows:

- Multiplex the data lines and then keep the clock signal transmitting to both.

- Multiplex the unidirectional clock signal and then keep the data lines going to both.

In your case, you want to hot swap the card by not selecting the SEL pin to be high; yes, it can be done in this fashion. If SEL is left floating, then the internal circuitry will pull all of your CMD and DATA lines high through 70K resistors and pull the clock signal low. Internal defaults set like this are functioning akin to the second recommended setup for handling multiple SD devices. In this case however, both devices will be disabled since neither will receive a clock. When you are ready to jumper the SEL pin, if you pull it high, the SD card you inserted in port B1 will receive the multiplexed clock and become active. If you pull SEL low, then the WiFi module on port B0 will receive the multiplexed clock and it will become active.

Operating this chip in the method you intend to, you shouldn’t have to disable power to the B1 port while conducting a hot swap. However, make sure that you follow the “Power-Up Considerations” on the 15th page of the datasheet for proper functionality.

If my recollection is correct, USH-Class 1 operates at 10MBps. Based on the “Timing Requirements” table for Vcca = 1.8V provided in the datasheet on page 8, you should have no issues running port B1 at that speed since. When Vccb = 1.8 or Vccb = 3.3 the data lines can push 120Mbps which is equivalent to 15MBps. Port B0 will support these same speeds if your WiFi module needs them.

Let me know if this answered all your questions and please verify the solution if it works for you. If you think of any additional questions, just let me know.

Best Regards,

Nick