minimum possible block size for MMC read or write

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vinodstanur

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what is the minimum possible block size for a MMC or SD card? I want to read or write to an MMC card using a PIC16F877A . So i want to know if its possible to set the block size as 64bytes instead of 512 bytes....
 

Hello,

The mimimum block size is always going to be 512 bytes. Use a pin compatible 18F device or use 2 arrays of 256 bytes.

The Flowcode FAT driver uses 2 x 256 byte arrays to get around this problem.
 

The RAM in the 16F877A is not enough.

You could use a buffer memory (such as a FRAM) where the data for the MMC could be stored temporarily, similar to a cache memory in a PC.

18F4620 or 18F2620 both have sufficient RAM and ROM to do the job.

18F4620 is pin compatible with 16F877A, if you want lower pin count then 18F2620 is good.

My suggestion, go in for the 18F device.

thanks
a
 
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