Units Of Data - Texas Instruments OMAP5912 Reference Manual

Table 99. Activity Shown in Figure 20
4.5

Units of Data

SPRU755B
In this example Ch1: PERIPH -> External memory, Ch2: PERIPH -> DARAM,
Ch4: DARAM -> Ext mem.
Port
DARAM
External memory
Peripherals
For each port in Figure 20, there is a channel that is connected to the service
chain but does not use the port. For example, the peripherals port is not used
by channel 4. If channel 4 is redefined to include the peripherals port as source
or destination, the port handles channel 4 according to its position and priority
in the service chain.
Four levels of data granularity are available when referring to a DMA transfer:
Byte: An 8-bit value. A byte is the smallest unit of data transferred in a DMA
-
channel.
Element: One or more bytes to be transferred as a unit. Depending on the
-
programmed data type, an element is an 8-bit, 16-bit, or a 32-bit value. An
element transfer cannot be interrupted: all of its bytes are transferred to
a port before another channel or the MPUI can take control of the port.
Frame: One or more elements to be transferred as a unit. A frame transfer
-
can be interrupted between element transfers.
Block: One or more frames to be transferred as a unit. Each channel can
-
transfer one block of data (once or multiple times). A block transfer can be
interrupted between frame transfers and element transfers.
For each of the six DMA channels, you can define the number of frames in a
block (with DMA_CFN ), the number of elements in a frame (with DMA_CEN),
and the number of bytes in an element (with the DATA_TYPE bits in
DMA_CSDP). For descriptions of DMA_CFN, DMA_CEN, DMA_CSDP, and
other registers of the DMA controller, see Section 4.22, Control Configuration
Registers.
This Port Arbitrates
Write access requests from channel 2
Read access requests from channel 4
Read or write access requests from the MPUI
Write access requests from channel 1
Write access requests from channel 4
Read or write access requests from the MPUI
Read access requests from channel 1
Read access requests from channel 2
Direct Memory Access (DMA) Support
DSP DMA
133