cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 
Highlighted
Advisor
Advisor
7,571 Views
Registered: ‎10-10-2014

what if I do not connect the SD WP pin to (E)MIO

Jump to solution

If I don't connect the SD card controller's Write Protect pin to an external MIO or EMIO pin, is the SD card 'write protected' or not from the point of view of the controller (asuming the card's own write protect switch is set to 'write enabled')?

 

So in the screenshot below, if I would remove MIO pin 50 by deselecting 'Write protect', would the SD card be writable? That would save me an MIO pin.

 

Also I know I can connect it to EMIO, and add a constant '0' to the pin (in my design I need the SD to be writable because I boot the kernel from the SD card, and it seems to expect a writable SD card). But I'm not sure if that's the best way for me, so I'd prefer to just leave it disconnected from the MIO.

 

So in other words, has the SD controller an internall weak pull-down or pull-up on this pin, so that - if left unconnected it takes a defined state?

 

SD card IO config.jpg

 

Actually, I have the same question for the CD pin :-)

 

** kudo if the answer was helpful. Accept as solution if your question is answered **
0 Kudos
1 Solution

Accepted Solutions
Highlighted
Xilinx Employee
Xilinx Employee
13,005 Views
Registered: ‎08-01-2008
check this ARs
http://www.xilinx.com/support/answers/61064.html
http://zedboard.org/sites/default/files/ZedBoard_HW_UG_v1_1.pdf
Thanks and Regards
Balkrishan
--------------------------------------------------------------------------------------------
Please mark the post as an answer "Accept as solution" in case it helped resolve your query.
Give kudos in case a post in case it guided to the solution.

View solution in original post

11 Replies
Highlighted
Scholar
Scholar
7,557 Views
Registered: ‎06-10-2008

I believe that using EMIO with a constant '0' is the only option, but I'm curious to hear otherwise.

Highlighted
Xilinx Employee
Xilinx Employee
13,006 Views
Registered: ‎08-01-2008
check this ARs
http://www.xilinx.com/support/answers/61064.html
http://zedboard.org/sites/default/files/ZedBoard_HW_UG_v1_1.pdf
Thanks and Regards
Balkrishan
--------------------------------------------------------------------------------------------
Please mark the post as an answer "Accept as solution" in case it helped resolve your query.
Give kudos in case a post in case it guided to the solution.

View solution in original post

Highlighted
Advisor
Advisor
7,521 Views
Registered: ‎10-10-2014

thanks @balkris, AR# 61064 is clear on that : the signal is required for the SD controller.

 

This info should added to the TRM, or at least the AR should be referred to in the TRM.

 

I ended up connecting WP to EMIO, and connect this EMIO to a constant IP block with '0' to permanently write enable the SD card. 

 

 

** kudo if the answer was helpful. Accept as solution if your question is answered **
0 Kudos
Highlighted
Scholar
Scholar
7,513 Views
Registered: ‎06-10-2008

When CD is not enabled in the Zynq peripheral configuration the FSBL could also set Card_detect_signal_detection in the Register Host_control_Power_control_Block_Gap_Control_Wakeup_control register and set Card_Detect_Test_Level as well. Unfortunately that is not what is generated. And there seem to be no such registers bits for WP.

Highlighted
Adventurer
Adventurer
7,459 Views
Registered: ‎11-09-2009

Hi,

Are these signals required for when eMMc is used also ?

I noticed that in picozed the CD is internally connected to GND

 

Is the WP also needed in case of eMMC ?

 

 

0 Kudos
Highlighted
Community Manager
Community Manager
7,426 Views
Registered: ‎07-23-2012
You can connect it to Gnd inside PL section
-----------------------------------------------------------------------------------------------
Please mark the post as "Accept as solution" if the information provided answers your query/resolves your issue.

Give Kudos to a post which you think is helpful.
0 Kudos
Highlighted
Scholar
Scholar
7,407 Views
Registered: ‎06-10-2008

@teroki wrote:

Are these signals required for when eMMc is used also ?

 


AFAIK they are required for eMMC as well. It's the host controller and/or software driver that needs them. And I don't think it knows of any difference between eMMC and (u)SD.

0 Kudos
Highlighted
Adventurer
Adventurer
7,379 Views
Registered: ‎11-09-2009

picozed only seems to use CD ?

 

0 Kudos
Highlighted
Advisor
Advisor
6,414 Views
Registered: ‎10-10-2014

@teroki, did you find an answer to the question if eMMC needs a similar WP line connected to GND? (through EMIO for example?)

 

@balkris, do you have an answer on this ? It's not mentioned in the AR (only for SD card)

** kudo if the answer was helpful. Accept as solution if your question is answered **
0 Kudos
Highlighted
Adventurer
Adventurer
3,931 Views
Registered: ‎11-09-2009

I got this answer

>>Since Vivado 2015.2, CD and WP are not necessary with the SDIO controller.

 

But we decides to put them both connected in our HW.

 

 

0 Kudos
Highlighted
Scholar
Scholar
3,921 Views
Registered: ‎06-10-2008

That is not my experience if you want to write to it from linux.

0 Kudos