Preliminary
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Registers
Table 9-18. Configuration Register (SD_CON) Field Descriptions (continued)
Bit
Field
Value
Description
18
BOOT_CF0
Boot Status Supported. This register is set when the CMD line needs to be forced to 0 for a
boot sequence. CMD line is driven to 0 after writing in SD_CMD. The line is released when
this bit field is de-asserted and aborts data transfer in case of a pending transaction.
Read 0
CMD line not forced.
Read 1
CMD line is released when it was previously forced to 0 by a boot sequence.
Write 0
CMD line forced to 0 is enabled.
Write 1
CMD line forced to 0 is enabled and will be active after writing into SD_CMD register.
17
BOOT_ACK
Book acknowledge received. When this bit is set the controller should receive a boot status on
DAT0 line after next command issued. If no status is received a data timeout will be
generated.
0
No acknowledge to be received.
1
A boot status will be received on DAT0 line after issuing a command.
16
CLKEXTFREE
External clock free running. This register is used to maintain card clock out of transfer
transaction to enable slave module (for example to generate a synchronous interrupt on
SD_DAT1). The Clock will be maintain only if SD_SYSCTL[2] CEN bit is set.
0
External card clock is cut off outside active transaction period.
1
External card clock is maintain even out of active transaction period only if SD_SYSCTL[2]
CEN bit is set.
15-12
Reserved
0
Reserved bit field. Do not write any value.
11
CTPL
Control Power for SD_DAT1 line (SD cards). By default, this bit is cleared to 0 and the host
controller automatically disables all the input buffers outside of a transaction to minimize the
leakage current.
SDIO cards. When this bit is set to 1, the host controller automatically disables all the input
buffers except the buffer of SD_DAT1 outside of a transaction in order to detect asynchronous
card interrupt on SD_DAT1 line and minimize the leakage current of the buffers.
0
Disable all the input buffers outside of a transaction.
1
Disable all the input buffers except the buffer of SD_DAT1 outside of a transaction.
10-9
DVAL
Debounce filter value (all cards). This register is used to define a debounce period to filter the
card detect input signal (SDCD). The usage of the card detect input signal (SDCD) is optional
and depends on the system integration and the type of the connector housing that
accommodates the card.
0
33 us debounce period
1h
231 us debounce period
2h
1 ms debounce period
3h
8.4 ms debounce period
8
WPP
Write protect polarity (SD and SDIO cards only). This bit selects the active level of the write
protect input signal (SDWP). The usage of the write protect input signal (SDWP) is optional
and depends on the system integration and the type of the connector housing that
accommodates the card.
0
Active high level
1
Active low level
7
CDP
Card detect polarity (all cards). This bit selects the active level of the write protect input signal
(SDWP). The usage of the write protect input signal (SDWP) is optional and depends on the
system integration and the type of the connector housing that accommodates the card.
0
Active high level
1
Active low level
6-5
Reserved
0
Reserved bit field. Do not write any value.
4
MODE
Mode select (all cards). This bit selects the functional mode.
0
Functional mode. Transfers to the SD/SDIO cards follow the card protocol. The clock is
enabled. SD transfers are operated under the control of the SD_CMD register.
1
SYSTEST mode. SYSTEST mode. The signal pins are configured as general-purpose
input/output and the 1024-byte buffer is configured as a stack memory accessible only by the
local host or system DMA. The pins retain their default type (input, output or in-out). SYSTEST
mode is operated under the control of the SYSTEST register.
3-2
Reserved
0
Reserved bit field. Do not write any value.
971
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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