Information

Enhanced Secure Digital Host Controller
MPC8308 PowerQUICC II Pro Processor Reference Manual, Rev. 1
11-42 Freescale Semiconductor
Figure 11-22. DMA CSB Interface Block
11.5.2.1 Internal DMA Request
If the watermark level is met in the data transfer and the internal DMA is enabled, the data buffer block
sends a DMA request to DMA engine. The delay of response from the internal DMA engine depends on
the system bus loading and the priority assigned to eSDHC. The DMA engine does not respond to the
request during its burst transfer, and is available as soon as the burst is over. The data buffer deasserts the
request once an access on the buffer is made. Upon access to the buffer by the internal DMA, the data
buffer updates its internal buffer pointer and when the watermark level is satisfied, another DMA request
is sent.
11.5.2.2 DMA Burst Length
DMA burst length is set to a default value to transfer the data into and out of the system bus. This value is
not programmable by the user.
11.5.2.3 CSB Master Interface
It is possible that the internal DMA engine fails during the data transfer. When an error occurs, the DMA
engine stops the transfer and goes to the idle state, while the internal data buffer stops working, too.
IRQSTAT[DMAE] is set to inform the driver.
Once the IRQSTAT[DMAE] interrupt is received, software should send CMD12 to abort the current
transfer and read DSADDR[DS_ADDR] to obtain the start address of the corrupted block. After the DMA
error is fixed, the software should apply a data reset and restart the transfer from this address to recover
the corrupted block.
11.5.3 SD Protocol Unit
The SD protocol unit deals with all SD protocol affairs and performs the following:
• Acts as the bridge between internal buffer and the SD bus
• Sends the command data and its argument serially
• Stores the serial response bit stream into corresponding registers
eSDHC Registers
System Address
R/W Indication
Error Indication
Buffer Control
Burst Length
Data Exchange
DMA Request
Interface
Master
Logic
DMA
Engine
Signal
Cluster
CSB
CSB