Description
Name
Bits
These bits indicate the second data buffer byte size. The
buffer size must be a multiple of four. When the buffer
size is not a multiple of four, the resulting behavior is
undefined. This field is not valid if DES0[4] is set to 1.
Buffer 2 Size (BS2)
25:13
Indicates the data buffer byte size, which must be a
multiple of four bytes. When the buffer size is not a
multiple of four, the resulting behavior is undefined. If
this field is 0, the DMA ignores the buffer and proceeds
to the next descriptor for a chain structure, or to the next
buffer for a dual-buffer structure.
If there is only one descriptor and only one buffer to be
programmed, you need to use only buffer 1 and not buffer
2.
Buffer 1 Size (BS1)
12:0
The DES2 descriptor field contains the address pointer to the data buffer.
Table 11-6: Internal DMA Controller DES2 Descriptor Field
†
Description
Name
Bits
These bits indicate the physical address of the first data
buffer. The internal DMA controller ignores DES2 [1:0],
because it only performs 32-bit aligned accesses.
Buffer Address Pointer 1 (BAP1)
31:0
The DES3 descriptor field contains the address pointer to the next descriptor if the present descriptor is not
the last descriptor in a chained descriptor structure or the second buffer address for a dual-buffer structure.
†
Table 11-7: Internal DMA Controller DES3 Descriptor Field
†
Description
Name
Bits
These bits indicate the physical address of the second
buffer when the dual-buffer structure is used. If the Second
Address Chained (DES0[4]) bit is set to 1, this address
contains the pointer to the physical memory where the
next descriptor is present.
If this is not the last descriptor, the next descriptor address
pointer must be aligned to 32 bits. Bits 1 and 0 are ignored.
Buffer Address Pointer 2 (BAP2) or
Next Descriptor Address
31:0
Host Bus Burst Access
The internal DMA controller attempts to issue fixed-length burst transfers on the master interface if configured
using the fixed burst bit (
fb
) of the
bmod
register. The maximum burst length is indicated and limited by
the programmable burst length (
pbl
) field of the
bmod
register. When descriptors are being fetched, the
master interface always presents a burst size of four to the interconnect.
†
SD/MMC Controller
Altera Corporation
cv_54011
Host Bus Burst Access
11-10
2013.12.30