Preliminary
Registers
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9.4.11 Transfer Length Configuration Register (SD_BLK)
This register shall be used for any card. SD_BLK[BLEN] is the block size register. SD_BLK[NBLK] is
the block count register.
The transfer length configuration register (SD_BLK) is shown in
and described in
.
Figure 9-39. Transfer Length Configuration Register (SD_BLK)
31
16
15
12
11
0
NBLK
Reserved
BLEN
R/W-0
R-0
R/W-0
LEGENDR/W = Read/Write; R = Read only; -n = value after reset
Table 9-21. Transfer Length Configuration Register (SD_BLK) Field Descriptions
Bit
Field
Value
Description
31-16
NBLK
Blocks count for current transfer. This register is enabled when Block count Enable
(SD_CMD[1] BCE bit) is set to 1 and is valid only for multiple block transfers. Setting the block
count to 0 results no data blocks being transferred.
NoteThe host controller decrements the block count after each block transfer and stops when
the count reaches zero.
This register can be accessed only if no transaction is executing (i.e., after a transaction has
stopped). Read operations during transfers may return an invalid value and write operation will
be ignored. In suspend context, the number of blocks yet to be transferred can be determined
by reading this register. When restoring transfer context prior to issuing a Resume command,
The local host shall restore the previously saved block count.
0
Stop count
1h
1 block
2h
2 blocks
FFFFh
65535 blocks
15-12
Reserved
0
Reserved bit field. Do not write any value.
11-0
BLEN
Transfer block size. This register specifies the block size for block data transfers. Read
operations during transfers may return an invalid value, and write operations are ignored.
When a CMD12 command is issued to stop the transfer, a read of the BLEN field after transfer
completion (SD_STAT[1] TC bit set to 1) will not return the true byte number of data length
while the stop occurs but the value written in this register before transfer is launched.
0
No data transfer
1h
1 byte block length
2h
2 bytes block length
3h
3 bytes block length
1FFh
511 bytes block length
200h
512 bytes block length
7FFh
2047 bytes block length
800h
2048 bytes block length
974
Secure Digital (SD)/—Secure Digital I/O (SDIO) Card Interface
SPRUGX9 – 15 April 2011
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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