Procedures for Common Operations 25.3.9MMC/SD Mode Multiple-Block Read Operation Using EDMA
To perform a multiple-block read,the same block length must be set in both the MMC/SD controller and the card.
The procedure for this operation is as follows:
1.Write the card’s relative address to the MMC argument registers(MMCARGH and MMCARGL).Load
the high part of the address to MMCARGH and the low part of the address to MMCARGL.
2.Read card CSD to determine the card's maximum block length.
3.Use the MMC command register(MMCCMD)to send the SET_BLOCKLEN command(if the block
length is different than the length used in the previous operation).The block length must be a multiple第三种温暖
of512bytes and less then the maximum block length specified in the CSD.
4.Reset the FIFO(FIFORST bit in MMCFIFOCTL).
5.Set the FIFO direction to receive(FIFODIR bit in MMCFIFOCTL).
6.Set the FIFO threshold(FIFOLEV bit in MMCFIFOCTL).
7.Set the access width(ACCWD bits in MMCFIFOCTL).
8.Set up DMA(DMA size needs to be greater than or equal to FIFOLEV setting).
9.Use MMCCMD to send the READ_MULTI_BLOCK command to the card.
10.Set the DMATRIG bit in MMCCMD to trigger the first data transfer.
上海劳动报11.Wait for DMA sequence to complete. 12.Use the MMC status register0(MMCST0)to check for errors.
13.Use MMCCMD to send the STOP_TRANSMISSION command.
25.3.10SDIO Card Function
To support the SDIO card,the following features are available in the MMC/SD controller:
•Read wait operation request
•Interrupt to CPU at the start of read wait operation
•Interrupt to CPU at the detection of SDIO interrupt
When in1-bit mode and the transfer clock(memory clock)is off,this peripheral cannot recognize an SDIO interrupt from SD_DATA1line.Two options are available to deal with this situation:
1.Do not turn off the memory clock in1-bit mode.The clock is enabled by the CLKEN bit in the MMC
memory clock control register(MMCCLK).
丙氨酸2.If the memory clock needs to be turned off,physically connect a GPIO signal and SD_DATA1,and use
the GPIO as an external interrupt input.When the memory clock is enabled,disable the GPIO interrupt and enable the SDIO interrupt.When the memory clock is disabled,enable the GPIO interrupt and
disable the SDIO interrupt by software.
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25.3.10.1SDIO Control Register(SDIOCTL)
The SDIO card control register(SDIOCTL)is used to configure the read wait operation using the
SD_DATA2line.
25.3.10.2SDIO Status Register0(SDIOST0)
The SDIO card status register0(SDIOST0)is used to check the status of the SD_DATA1signal,check the status of being in an interrupt period,or check the status of being in a read wait operation.
Procedures for Common Operations 25.3.2MMC/SD Mode Single-Block Write Operation Using CPU
To perform a single-block write,the block length must be512bytes and the same length needs to be set in both the MMC/SD controller and the memory card.The procedure for this operation is:
1.Write the card’s relative address to the MMC argument registers(MMCARGH and MMCARGL).Load
the higher part of the address to MMCARGH and the low part of the address to MMCARGL.
2.Use the MMC command register(MMCCMD)to send the SELECT/DESELECT_CARD broadcast
command.This selects the addressed card and deselects the others.
刷式密封3.Write the destination start address to the MMC argument registers.Load the high part to the 教育手拉手
论坛MMCARGH register and the low part to MMCARGL. 4.Read the card CSD to determine the card’s maximum block length.
5.Use MMCCMD to send the SET_BLOCKLEN command(if the block length is different than the len
gth
used in the previous operation).The block length must be a multiple of512bytes and less then the
maximum block length specified in the CSD.
6.Reset the FIFO(FIFORST bit in MMCFIFOCTL).
7.Set the FIFO direction to transmit(FIFODIR bit in MMCFIFOCTL).
8.Set the access width(ACCWD bits in MMCFIFOCTL).
9.Enable the MMC interrupt.
10.Enable the DXRDYINT interrupt.
11.Write the first32bytes of the data block to the data transmit register(MMCDXR).
12.Use MMCCMD to send the WRITE_BLOCK command to the card.
13.Set the DMATRIG bit in MMCCMD to trigger the first data transfer.
14.Wait for the MMC interrupt.
15.Use the MMC status register0(MMCST0)to check for errors and the status of the FIFO.If all of the
data has not been written and if the FIFO is not full,go to Step16.If all of the data has been written,
stop.
16.Write the next n bytes(this depends on the setting of the FIFOLEV bit in MMCFIFOCTL:0=32bytes,
1=64bytes)of the data block to the MMC data transmit register(MMCDXR)and return to Step14.
The sequence of events in this operation is shown in Figure25-13.
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