Kingston microSD SPI initialization fails on ACMD41

Hi please ,can i have your hints?

i have problems trying to initialize Kingston 8GB microSDHC card at 3.3V. At electrical level it looks ok,i wrote a low level driver on a board that i can easily debug,and i can check the signals with DSO-LA.

The card has a detailed datasheet

formatting link

I issued the preliminary sequence at low clock speed with CS and MOSI high,in order to enter in SPI commands mode.

All the comands are issued with CS always low low

The commands(all with calculate checksum)looks working,i have coherent answers ,for example CMD08 with argument 0x000001AA and CRC, i have the response 0x1 followed by the echo of the argument. The problem is with ACMD 41,datasheet says at page 10: "2If the signalling level is 3.3V, host continues to issue ACMD41 with HCS=1 and S18R=1 until the response indicates ready. If bit 31 indicates ready, host needs to check CCS and S18A"

The flowchart at page 11 shows that bits in the answer Busy (bit 3)1 CCS (bit 30) and S18A (bit 24) should be 1,but i have the first received byte[31:24]=0x00 so all these bits are 0. If anyone faced this specific situation i would thank in advance for help. Thanks, Diego , Milan,Italy

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