In my case I am locked to a MCU that only supports SPI, and it's QSPI has hardcoded commands only working with NOR flash. (Yes I know, why did they do that!!!)
QSPI != SDIO, these are completely different protocols. MicroSD cards talk SDIO, but not QSPI, NOR flash is the opposite - it talks QSPI, but not SDIO.
I think you misunderstood my statement.
I know very well they are not the same, and I assumed everyone else did too. I am stating my MCU does not support SDIO although they did supply a QSPI hardware unit.
My point was that they did not even let you encode custom command sets or specify commands for the hardware so it is completely locked to NOR flash. This is a shame as a lot of NAND flash have a NOR compatible mode that just need a few bytes changed in command set to be compatible. Thus I am looking for a way to use the SD cards, preferably in LV mode (not just LVS) and this is where the LVS detection comes in. Cards that support LVS detection is one step closer to LV mode as they allow init at 1.8v signal levels so you do not need level shifters. You would specify 2.7-2.8v voltage bracket to the card for supply (allowing it to run of lower voltage battery than 3.3v would) and you signal to the card at 1.8v activating the LVS detection. In my case I wanted to activate the SPI mode so I can leverage the DMA driven SPI hardware at least.
I made tests for this and can indeed activate LVS mode while signaling at 1.8v but it does not respond to SPI activation.
Thus I made code that allow for verifying that I can talk to it in 1-bit SD mode, and at 3.3v this code works and card responds to CMD8, CMD55 and ACMD41 so far. There is no response from CMD0.
Changing to 1.8v there is no response. If I run LVS detection first the card responds in about 2.3ms which is within the required 5ms, but later 1-bit SD-mode commands do not result in any responses.
This is very sad as it would open up the use of SD cards a lot.