mmchs-063
clk
cmd
ACMD12
dat
S
E
Last data block
Next data block
S
E
left border case
right border case
cmd
ACMD12
S
E
1 2
3 4 5 6
7
Public Version
MMC/SD/SDIO Functional Description
www.ti.com
24.4.6.2 Autocommand 12 Timings During Read Transfer
With UHS very high speed cards gap timing between 2 successive cards has been extended to 4 cycles
instead of 2. By the way it gives more flexibility for Host Auto CMD12 arrival in order to receive the last
complete and reliable block. MMCHS controller only follows the 'Left Border Case' defined by SD UHS
specification.
shows ACMD12 timings during read transfer.
Figure 24-30. Autocommand 12 Timings During Read Transfer
The Auto CMD12 arrival sent by the Host controller is not sensitive to the MMC bus configuration whether
it is DDR or standard transfer and whether it is a 1,4 or 8 bit bus width transfer.
24.4.7 Transfer Stop
Whenever a transfer is initiated, the transmission may be willed to stop whereas it is still not finished.
Several cases can be faced depending on the transfer type:
•
Multiple blocks oriented transfers (for which transfer length is known)
•
Continuous stream transfers (which have an infinite length)
NOTE:
Since the MMC/SD/SDIOi controller manages transfers based on a block granularity, the
buffer will accept a block only if there is enough space to completely store it. Consequently, if
a block is pending in the buffer, no command will be sent to the card because the card clock
will be shut off by the controller.
The MMC/SD/SDIOi controller includes two features which makes a transfer stop more convenient and
easier to manage:
•
Auto CMD12 (for MMC and SD only).
This feature is enabled by setting the MMCi.
[2] ACEN bit to 0x1 (this setting is relevant
for a MMC/SD transfer with a known number of blocks to transfer). When the Auto CMD12 feature is
enabled, the MMC/SD/SDIOi controller will automatically issue a CMD12 command when the expected
number of blocks has been exchanged.
•
Stop at block gap
This feature is enabled by setting the MMCi.
[16] SBGR bit to 0x1. When enabled, this
capability holds the transfer on until the end of a block boundary. If a stop transmission is needed,
software can use this pause to send a CMD12 to the card.
NOTE:
For MMC and SD cards, the stop at block gap feature is not supported in READ mode.
For SDIO cards, this setting can be supported in READ mode if the card has a read wait
capability.
3394
MMC/SD/SDIO Card Interface
SWPU177N – December 2009 – Revised November 2010
Copyright © 2009–2010, Texas Instruments Incorporated
Содержание OMAP36 Series
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Страница 692: ...692 MPU Subsystem SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 1084: ...1084 IVA2 2 Subsystem SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 1990: ...1990 2D 3D Graphics Accelerator SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 2334: ...2334 Memory Subsystem SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 2700: ...2700 Memory Management Units SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 2868: ...2868 HDQ 1 Wire SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 2974: ...2974 UART IrDA CIR SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 3054: ...3054 Multichannel SPI SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 3462: ...3462 MMC SD SDIO Card Interface SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 3508: ...3508 General Purpose Interface SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 3584: ...3584 Initialization SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 3648: ...3648 Debug and Emulation SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...