Addressing Modes - Texas Instruments OMAP5912 Reference Manual

System DMA
3.1.10

Addressing Modes

Table 20. Logical Channel Type Address Mode Summary
44 Direct Memory Access (DMA) Support
An addressing mode is an address computation algorithm that a DMA channel
uses to find where to access data. The system DMA supports four types of
addressing modes:
Constant index mode
-
Post-incremented mode
-
Single-indexed (element index) mode
-
Double-indexed (element and frame index) mode
-
Based on LCh types, the summary of addressing modes is as follows:
Addressing Mode
Constant
Post-incremented
Single-indexed
Double-indexed
The amount of data (block size) to be transferred is programmed in bytes.
The data block to transfer is split into frames and elements. The data block size
in bytes can be expressed as:
BSi = FN x EN x ES
where:
BSi: The block size in bytes.
FN: The number of frames in the block, 1 ≤ FN ≤ 65535 (unsigned) which
is defined in the DMA channel frame number register (DMA_CFN).
EN: The number of elements per frame, 1 ≤ EN ≤ 65535 (unsigned) which
is defined in each DMA channel element number register (DMA_CEN).
ES: The number of bytes per element, ES ∈ {1, 2, 4}, which is defined with
the field DATA_TYPE in register DMA channel source destination parame-
ters (DMA_CSDP).
A frame size in bytes: FSi = ES x EN.
Setting FN or EN equal to 0 is not allowed, because it causes undefined
effects.
LCh-P and LCh-PD
Peripheral
Port
Memory Port
√ √
√ √
√
√
LCh-2D LCh-G
√ √
√ √
√ √
√ √
SPRU755B