Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

minimum possible block size for MMC read or write

Status
Not open for further replies.

vinodstanur

Advanced Member level 3
Joined
Oct 31, 2009
Messages
750
Helped
114
Reputation
234
Reaction score
114
Trophy points
1,333
Location
Kerala (INDIA)
Activity points
7,049
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....
 

assasinsareus

Junior Member level 3
Joined
Jul 21, 2010
Messages
25
Helped
3
Reputation
6
Reaction score
2
Trophy points
1,283
Activity points
1,428
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.
 

arbj

Full Member level 4
Joined
Oct 5, 2008
Messages
238
Helped
31
Reputation
62
Reaction score
20
Trophy points
1,298
Activity points
2,601
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
 
Last edited:

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top