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_shifters1.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_modules1.png