MMC/SD Host Controller
7-148
This register configures the buffer threshold level of the thirty two 16-bit-word
FIFO and enables DMA transfers.
Table 7–109. MMC Buffer Configuration Register (MMC_BUF)
Bit
Name
Description
15
RX_DMA_En
Receive DMA channel enable
14 –13
Reserved
12 –8
AF_Level
Buffer almost full level
7
TX_DMA_En
Transmit DMA channel enable
6–5
Reserved
4 –0
AE_Level
Buffer almost empty level
Receive DMA Channel Enable (RX_DMA_En)
When this bit (15) is set to 1, the receive DMA channel is enabled and the
A_Full status bit is forced to 0 by the core irrespectively of AF_level setting (see
Table 7–109).
-
0: Receive DMA channel disabled
-
1: Receive DMA channel enabled
Value after reset is low.
Buffer Almost Full Level (AF_Level)
This register (bits 12-8) holds the programmable almost full level value used
to determine almost full buffer condition. If you want an interrupt or a DMA read
request to be issued during a read operation when the data buffer holds
n words of 16 bits, then AF_Level must be set with n-1.
-
0x00 1 16-bit word (2 bytes)
-
0x1E: 31 16-bit word (62 bytes)
-
0x1F: 32 16-bit word (64 bytes)
Values after reset are 0x1F.