Data Transmit
†
• No CRC status—during a write data transfer, if the CRC status start bit is not received for two clock
cycles after the end bit of the data block is sent out, the data path performs the following actions:
†
• Signals no CRC status error to the BIU
†
• Terminates further data transfer
†
• Signals data transfer done to the BIU
†
• Negative CRC—if the CRC status received after the write data block is negative (that is, not 0b010), the
data path signals a data CRC error to the BIU and continues with the data transfer.
†
• Data starvation due to empty FIFO buffer—if the FIFO buffer becomes empty during a write data
transmission, or if the card clock stopped and the FIFO buffer remains empty for a data-timeout number
of clock cycles, the data path signals a data-starvation error to the BIU and the data path continues to
wait for data in the FIFO buffer.
†
Data Receive
• Data timeout—during a read-data transfer, if the data start bit is not received before the number of clock
cycles specified in the timeout register, the data path does the following action:
†
• Signals a data-timeout error to the BIU
†
• Terminates further data transfer
†
• Signals data transfer done to BIU
†
• Data SBE—during a 4-bit or 8-bit read-data transfer, if the all-bit data line does not have a start bit, the
data path signals a data SBE to the BIU and waits for a data timeout, after which it signals that the data
transfer is done.
†
• Data CRC error—during a read-data-block transfer, if the CRC-16 received does not match with the
internally generated CRC-16, the data path signals a data CRC error to the BIU and continues with the
data transfer.
†
• Data EBE—during a read-data transfer, if the end bit of the received data is not 1, the data path signals
an EBE to the BIU, terminates further data transfer, and signals to the BIU that the data transfer is done.
†
• Data starvation due to FIFO buffer full—during a read data transmission and when the FIFO buffer
becomes full, the card clock stops. If the FIFO buffer remains full for a data-timeout number of clock
cycles, the data path signals a data starvation error to the BIU, by setting the data starvation host timeout
bit (
hto
) in
rintsts
register to 1, and the data path continues to wait for the FIFO buffer to empty.
†
Clocks
Table 11-14: SD/MMC Controller Clocks
Description
Direction
Clock Name
Clock for SD/MMC controller BIU
In
l4_mp_clk
Clock for SD/MMC controller
In
sdmmc_clk
Generated output clock for card
Out
sdmmc_cclk_out
Divide-by-four clock of
sdmmc_clk
Internal
sdmmc_clk_divided
Altera Corporation
SD/MMC Controller
11-27
Data Transmit
†
cv_54011
2013.12.30