Espressif ESP32 Technical Reference Manual page 202

9 SD/MMC Host Controller
Bits
3
2
1
0
The DES1 element contains the buffer size.
Bits
31:26
25:13
12:0
The DES2 element contains the address pointer to the data buffer.
Bits
31:0
The DES3 element contains the address pointer to the next descriptor if the present descriptor is not the last
one in a chained descriptor structure.
Bits
31:0
Espressif Systems
Name
FD (First Descriptor)
LD (Last Descriptor)
DIC (Disable Interrupt
on Completion)
Reserved
Table 9-3. DES1
Name
Reserved
Reserved
BS1 (Buffer 1 Size)
Table 9-4. DES2
Name
Buffer Address Pointer 1
Table 9-5. DES3
Name
Next Descriptor Address
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Description
When set, this bit indicates that this descriptor con-
tains the first buffer of the data. If the size of the first
buffer is 0, the Next Descriptor contains the begin-
ning of the data.
This bit is associated with the last block of a DMA
transfer. When set, the bit indicates that the buffers
pointed by this descriptor are the last buffers of the
data. After this descriptor is completed, the remain-
ing byte count is 0. In other words, after the descrip-
tor with the LD bit set is completed, the remaining
byte count should be 0.
When set, this bit will prevent the setting of the TI/RI
bit of the DMAC Status Register (IDSTS) for the data
that ends in the buffer pointed by this descriptor.
Reserved
Description
Reserved
Reserved
Indicates the data buffer byte size, which must be a
multiple of four. In the case where the buffer size is
not a multiple of four, the resulting behavior is unde-
fined. This field should not be zero.
Description
These bits indicate the physical address of the data
buffer.
Description
If the Second Address Chained (DES0[4]) bit is set,
then this address contains the pointer to the physical
memory where the Next Descriptor is present.
202 ESP32 TRM (Version 5.2)