Portion A
Portion B
MEM_SIZE/8
Interconnect clock domain
Interface (card) clock domain
3’
3
4’
4
Read from
SD_DATA
Read from card
4
occurs only after
3
4
When
is completed,
4’
occurs only after
3’
Portion A
Portion B
MEM_SIZE/8
Read from
SD_DATA
Read from card
are two different transfers that occur at the same time.
and
Read
to
the card
SD_CMD[DDIR]=1
Interconnect bus
Interconnect bus
32 bits
32 bits
32 bits
32 bits
Card bus
Card bus
Functional Description
Figure 18-20. Buffer Management for a Read
18.3.7.1.1 Memory Size, Block Length, and Buffer Management Relationship
The maximum block length and buffer management that can be targeted by system depend on memory
depth setting.
Table 18-12. Memory Size, BLEN, and Buffer Relationship
Memory Size([5:2] MEMSIZE in bytes)
512
1024
2048
4096
Maximum block length supported
512
1024
2048
2048
Double-buffering for maximum block
N/A
BLEN <= 512
BLEN <= 1024
BLEN <= 2048
length
Single-buffering for block length
BLEN<=512
512 < BLEN <=
1024 < BLEN <=
N/A
1024
2048
3368
Multimedia Card (MMC)
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated