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Registered: ‎10-21-2010

Zynq SDIO CMD line conflict over MIO



I'm bringing up a new board with the Zynq 7020 and trying to boot from the SD card. Silicon revision is 3.0 and i'm working with ISE 14.7. The SD card is connected to pins 40-47, with CD and WP on MIO47/46 tied to GND.


I am faced with two problems:


1) bootrom doesn't start the SD interface (SD clock does not toggle at boot); debugging with xmd confirmed that the boot mode is correctly detected by the bootrom, which reports error 200A (could not access boot image on SD card)


2) when starting up the FSBL into DDR through JTAG, it also fails to access the SD card. This time however it starts up the SD clock to 200 khz and issues 6 bits of the command (01 + 4 bits of the command code) before releasing the CMD line and reporting a CMD conflict error (INT_STATUS register at 0xe0100030 has value 0x00038000). I attached a scope capture of the behaviour.


The problem is identical to this post:


except that we access the SD card through MIO40-47 instead of EMIO.


I should add that the SD bus goes through a TXS0612 level translator to the SD connector. The behaviour is unchanged when removing the level translator (pins remain open), when activating MIO40-45 pullups, or when setting the pin slew rate to fast/slow.


Any help is greatly appreciated.


Best regards,


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