Preliminary
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Registers
9.4.18 Data Register (SD_DATA)
This register is the 32-bit entry point of the buffer for read or write data transfers. The buffer size is
32bitsx256(1024 bytes). Bytes within a word are stored and read in little endian format. This buffer can
be used as two 512 byte buffers to transfer data efficiently without reducing the throughput.
Sequential and contiguous access is necessary to increment the pointer correctly. Random or skipped
access is not allowed. In little endian, if the local host accesses this register byte-wise or 16bit-wise, the
least significant byte (bits [7:0]) must always be written/read first. The update of the buffer address is
done on the most significant byte write for full 32-bit DATA register or on the most significant byte of the
last word of block transfer.
Example 1Byte or 16-bit access
•
Mbyteen[3:0]=0001 (1-byte) => Mbyteen[3:0]=0010 (1-byte) => Mbyteen[3:0]=1100 (2-bytes) OK
•
Mbyteen[3:0]=0001 (1-byte) => Mbyteen[3:0]=0010 (1-byte) => Mbyteen[3:0]=0100 (1-byte) OK
•
Mbyteen[3:0]=0001 (1-byte) => Mbyteen[3:0]=0010 (1-byte) => Mbyteen[3:0]=1000 (1-byte) Bad
The data register (SD_DATA) is shown in
and described in
.
Figure 9-46. Data Register (SD_DATA)
31
0
DATA
R/W-0
LEGENDR/W = Read/Write; R = Read only; -n = value after reset
Table 9-28. Data Register (SD_DATA) Field Descriptions
Bit
Field
Value
Description
31-0
DATA
Data register [31:0]. In functional mode (SD_CON[4] MODE bit set to the default value 0):
A read access to this register is allowed only when the buffer read enable status is set to 1
(SD_PSTATE[11] BRE bit), otherwise a bad access (SD_STAT[29] BADA bit) is signaled.
A write access to this register is allowed only when the buffer write enable status is set to 1
(SD_PSTATE[10] BWE bit), otherwise a bad access (SD_STAT[29] BADA bit) is signaled and the
data is not written.
981
SPRUGX9 – 15 April 2011
Secure Digital (SD)/—Secure Digital I/O (SDIO) Card Interface
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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