3.9. SDIO Interfaces

Pin Signal Description type I/O
51, 95 SD1_CD SD2_CD SD Card Detect – connected to a GPIO VDDIO I
52, 96 SD1_D[0] SD2_D[0] SD Data bidirectional signals VDDIO I/O
53, 97 SD1_D[1] SD2_D[1]
54, 98 SD1_D[2] SD2_D[2]
55, 99 SD1_D[3] SD2_D[3]
56, 100 SD1_CMD SD2_CMD SD Command bidirectional signal VDDIO I/O
57, 101 SD1_CLK SD2_CLK SD Output Clock. VDDIO O
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.

3.9.1. 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.

../../_images/sd_card_level_shifters.png

3.9.2. 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.

../../_images/sd_card_modules.png