SDIO Interfaces
================

+------+-----------+--------------------------------------------+-------------+-----------+
| Pin  | Signal    | Description                                | type        | I/O       |
+======+===========+============================================+=============+===========+
| 51,  | SD1_CD    | SD Card Detect – connected to a GPIO       | VDDIO       | I         |
| 95   | SD2_CD    |                                            |             |           |
+------+-----------+--------------------------------------------+-------------+-----------+
| 52,  | SD1_D[0]  | SD Data bidirectional signals              | VDDIO       | I/O       |
| 96   | SD2_D[0]  |                                            |             |           |
+------+-----------+                                            +             +           +
| 53,  | SD1_D[1]  |                                            |             |           |
| 97   | SD2_D[1]  |                                            |             |           |
+------+-----------+                                            +             +           +
| 54,  | SD1_D[2]  |                                            |             |           |
| 98   | SD2_D[2]  |                                            |             |           |
+------+-----------+                                            +             +           +
| 55,  | SD1_D[3]  |                                            |             |           |
| 99   | SD2_D[3]  |                                            |             |           |
+------+-----------+--------------------------------------------+-------------+-----------+
| 56,  | SD1_CMD   | SD Command bidirectional signal            | VDDIO       | I/O       |
| 100  | SD2_CMD   |                                            |             |           |
+------+-----------+--------------------------------------------+-------------+-----------+
| 57,  | SD1_CLK   | SD Output Clock.                           | VDDIO       | O         |
| 101  | SD2_CLK   |                                            |             |           |
+------+-----------+--------------------------------------------+-------------+-----------+
| **Module**       | **Remark**                                                           |
+------------------+----------------------------------------------------------------------+
| TX25, TX28, TX48 | Only one SD-Card available on standard pinout, SD Interface 2 is not |
|                  | used / not connected.                                                |
+------------------+----------------------------------------------------------------------+
| TX28             | Pin 101 is used as ENET_CLK.                                         |
+------------------+----------------------------------------------------------------------+

The TX pinout provides two dedicated SDIO interfaces. SDIO stands for Secure Digital Input Output which can also be used for SD-Memory-Cards.

SD-Card example diagram using level shifters
---------------------------------------------

No external pullups are needed here. Each port of the TXS0108E has an internal pull-up resistor. These have a value of 40 kΩ when the output is driving low and a value of 4 k Ω when the output is driving high. Unfortunately the card detect feature commonly used for Micro-SD cards on DAT3/CD cannot be used. A dedicated card detect switch is required.

.. figure:: ../images/sd_card_level_shifters.png
   :align: center

SD-Card example diagram only for 3.3V modules
----------------------------------------------

Either the use of the processor internal pullups or the use of pullups on the baseboard is possible.

.. figure:: ../images/sd_card_modules.png
   :align: center