Information

Enhanced Secure Digital Host Controller
MPC8308 PowerQUICC II Pro Processor Reference Manual, Rev. 1
Freescale Semiconductor 11-41
only restriction is from the external card since it may not support such a large block or a partial block
access that is not an integer multiple of 512 bytes.
11.5.1.4 Dividing Large Data Transfer
This SDIO command CMD53 definition limits the maximum data size of data transfers according to the
following formula:
Maximum data size = (block size)  (block count) Eqn. 11-2
The length of a multiple block transfer must be in block size units. If the total data length cannot be divided
evenly to a multiple of the block size, then there are two ways to transfer the data depending on the function
and card design.
• The card driver splits the transaction. The remainder of block size data is then transferred using a
single block command at the end.
• Add dummy data in the last block to fill the block size. The card must remove the dummy data.
See Figure 11-21 for an example of dividing large data transfers. Although the eSDHC supports a block
size of up to 4096 bytes, the example below illustrates a maximum of 64 bytes where the data must be
divided.
Figure 11-21. Example of Dividing a Large Data Transfer
11.5.2 DMA CSB Interface
The internal DMA implements a DMA engine and CSB master. When the internal DMA is enabled
(XFERTYP[DMAEN] is set), the buffer interrupt status bits are still set if they are enabled. To avoid
setting them, clear IRQSTATEN[BWRSEN, BRRSEN]. See Figure 11-22 for illustration of the DMA
CSB interface block. The internal DMA must not be used to read (or write) data if the data will be written
(or read) by the CPU through the DATPORT register.
802.11
MAC Header
IV
544-bytes WLAN Frame
Data
64-bytes
WLAN Frame is divided equally into 64-byte blocks plus the remainder 32-bytes
Data
64-bytes
Data
64-bytes
SDIO Data
Block 1
SDIO Data
Block 2
SDIO Data
Block 8
Eight 64-byte blocks are sent in Block Transfer Mode and the remainder
32-bytes are sent in Byte Transfer Mode
Frame Body ICV FCS
Data
32-bytes
SDIO Data
32-bytes
SDIO Data
Block 1
SDIO Data
Block 2
SDIO Data
Block 8
CMD53
SDIO Data
32-bytes
CMD53
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