SDCARD_CD# in SD interface

Dear Nvidia,

The JTX1 SOM is having SDCARD_CD# pin and SDCARD_PWR_EN pin .Is this pin SDCARD_CD# used for detecting the presence of card and enabling the power to the device through the power control switch using SDCARD_PWR_EN or for detecting the presence of the card alone and configuring the sd mode

In SD CARD I don’t have the Card detect pin which is a mechanical switch connecting to ground (any way not connected to sd card ) when inserted
so can I pull down this pin to ground by default since as per standard DATA3/CD is used for detection and configuration of mode is this ok for detecting SD card ?
if i use in this way will i be able to control the power through SDCARD_PWR_EN this pin ?

In current TX1 design, SDCARD_CD# is for card plug-in detection and inform TX1 to enable power supply to SD card. Current SD card connector on carrier board supports this detection. This function has nothing with SD card itself.

If you use SD card connector without CD# pin, you need to change the circuit design to use DAT3/CD as card detection – powering supply SD connector directly with system 3.3V is must, which means no need SDCARD_CD# and SDCARD_OWR_EN.

Hi Sir

Thank you for the reply

According to SD card spec, DAT3 pin can be used for card detection purpose.

changing the circuit deign in your reply means

Do I have to connect the DATA 3 pin of SD card to the CD pin of the JTX1 for detection ?
or data 3 pin in JTX1 can find the pull up present in the card end on the line and identify that card is inserted?
how does the detection work without card detect pin ?(since u have mentioned CD in TX1 is enabling power to card and then only TX1 can sense pull up in data3 line )how to make vcc enabled by default ?
can I pull card detect pin low always since the CD pin in JTX1 is not used ?

SDCARD_CD# is for hot-plug detection.

CD/DAT3 pin has internal PU in SD card, it can be used to do general initial card detection or hot-plug detection, if it is used as hot-plug, the power supply should be always on after system boot up and also need to connect it to dedicate INT pin which is high-enabled or thru an inverter to low-enabled INT pin. For details please check SD card protocol first and search some similar example circuit designs on internet as reference.

For all above changes in HW/SW that are violated to TX1 reference design, we can not guarantee and need you to do tuning by yourself.


Thanks for your reply sir

In my case i have connected VCC directly to the card so when card is inserted the data 3 line will be pulled up in the card end so TX1 can detect the card using this

I have checked this reference implementation pg-19

But my query is CD# pin if unused for card detection,what should be the default state ?

Leave it unconnected if unused.