
mmchs-043
Portion A (512 bytes)
Portion B (512 bytes)
128 words
128 words
System (L4) clock domain
Interface (card) clock domain
3’
3
4’
4
Read from
MMCHS_DATA
Read from card
4
occurs only after
3
4
When
is completed,
4’
occurs only after
3’
Portion A (512 bytes)
Portion B (512 bytes)
128 words
128 words
Read from
MMCHS_DATA
Read from card
are two different transfers that occur at the same time.
and
Read
to
the card
MMCHS_CMD[DDIR]=1
L4interconnectbus
L4interconnectbus
32bits
32bits
32bits
32bits
Cardbus
Cardbus
Public Version
MMC/SD/SDIO Functional Description
www.ti.com
Figure 24-22. Buffer Management for a Read
•
When the size of the data block to transfer is larger than 512 bytes, meaning the value written in BLEN
is 0x201 or larger, only one data transfer can occur from one data bus to the other data bus at a time.
The MMC/SD/SDIOi host controller uses the entire data buffer as a single 1024-byte portion.
In this mode, a bad access (MMCi.
[29] BADA) is signaled when two data transfers
occur from one data bus to the other data bus and vice versa at the same time.
24.4.3.1.1 Data Buffer Status
The data buffer status is defined in the following interrupt status register and status register:
•
Interrupt status registers (see
):
–
[29] BADA: Bad access to data space
–
[5] BRR: Buffer read ready
–
[4] BWR: Buffer write ready
•
Status registers (see
–
[11] BRE: Buffer read enable
–
[10] BWE: Buffer write enable
3388
MMC/SD/SDIO Card Interface
SWPU177N – December 2009 – Revised November 2010
Copyright © 2009–2010, Texas Instruments Incorporated