Question on CRC check in SD Card

[musfiq]

hello friends,

i am working on a project where we are using the SD card with SD bus mode

i have 3 questions regarding to CRC checking

1. Let i am reading a Data block of 512 bytes. It starts with a startbit (0) and then 512 bytes comes in sequence. Now, is the CRC16 check over the block includes the startbit, ie, total (1 bit + 512 bytes) ?

2. Let i am writing a data block of 512 bytes. I will first give a start bit(0) then the 512 bytes in sequence. Now, again, is the CRC16 calculation includes the startbit(0) or just plainly over the 512 bytes of data ?

3. Do i need to erase a data block before writing a new block there ?

That's all.
thanks a lot friends

 

[bateAz]

I am usin SD Cards with SD bus mode (only 1 data wire, not 4 ).
1. Leading bit is not taken in care when calculating CRC. You make check it yourself by simply reading one 512B block and compare the CRC returned by the card.
2. Errasing is not nessessary. You may put 'write ' command any time CD Card is not bussy. The SDC controller built in the card will do errasing for You.
'Errase' will decrease the 'write' command duration.

 

[santhu456]

Hi ,,,

I have a doubt on sd card memory ,, like by using CSD register parameter values we can find out how many sectors, capacity of card and block length,,, but how many blocks are present?? and how can we know the address of each block while reading or writing from/into the memory card???

please help on this????

Thank you...