Constant Addressing Mode - Texas Instruments OMAP5912 Reference Manual

DSP DMA
4.9.2

Constant Addressing Mode

138 Direct Memory Access (DMA) Support
The byte size of this data block is:
BS = FN x EN x ES
where:
BS is the block size in bytes.
FN is the number of frames in the block, 1 . FB . 65535.
EN is the number of elements per frame, 1 . EN . 65535.
ES is the number of bytes per element, ES . {1, 2, 4}.
An element can be:
8-bit scalar data, s8
-
16-bit scalar data, s16
-
32-bit scalar data, s32
-
s8, s16, and s32 are the types of the data transferred in a channel. FN, EN,
and ES (or DATA_TYPE) are extracted from the configuration registers of the
channel.
To set up a channel for a transfer, the software must program two addressing
modes:
Source addressing
-
Destination addressing
-
The modes work independently. For example, to transfer data from a TIPB
serial port to internal memory, the source-addressing mode is constant (for
example, when the read operation must be done at a unique register address)
and the destination addressing mode is post-incremented.
The number of frames, the number of elements, and the element size are the
same for source and destination. Each of the following algorithms describes
address computation for each byte of the transfer.
Address remains constant.
a( i) = SA, 0 . i . BS – 1
where:
a(i) is the address of the byte number i within the transfer.
SA is the start address of the transfer.
BS is the block size in bytes.
SPRU755B