MMC/SD Host Controller
7-138
Buffer Almost Full (A_Full)
The core automatically sets this bit (10) during a read operation to the card
when the level is above the threshold value set in MMC_BUFF:AF_Level reg-
ister bits. This bit indicates that the memory card has filled out the buffer to the
specified level and that the local host needs to empty the buffer by reading it.
If the DMA receive mode is enabled, this bit is never set; instead a DMA RX
request to the main DMA controller of the system is generated.
The A_Full status bit and DMA RX request are generated under the same
conditions. Once set, the core internally masks a new set condition till the local
host has performed [AF1] read access(es) from the FIFO.
AF_Level is the decimal equivalent set binary value (0 – 31).
-
0: No action or buffer is below or equal almost full level.
-
1: Buffer almost full
Value after reset is low.
Command CRC Error (Cmd_CRC)
MMC/SD mode only.
The core automatically sets this bit (8) if there is a CRC7 error in the command
response (bits 7:1 of all response types except type R3). A CMD1 (MMC) or
ACDM41 (SD) cannot trigger a CRC 7 error.
In SPI or SYSTEST modes, this bit has no meaning and always reads as 0
-
0: No action or no CRC7 error
-
1: CRC7 error
Value after reset is low.
Command Time-out Error (Cmd_timeout)
MMC/SD mode only.
The core automatically sets this bit (7) if the card does not respond within the
specified number of command time-out clock cycles (CTO) that is set in
MMC_CTO register (see N
CR
timing requirements) to any command requiring
a response.
If this bit is set after a command time-out, clearing this bit automatically stops
the MMC clock and force the controller state to idle.