Read/Write Synchronization - Texas Instruments OMAP5910 Reference Manual

Table 49. Read/Write Synchronization
SYNC Field of DMACCR Source Port
00000b
Not 00000b
Not 00000b
Not 00000b
SPRU890A
There are three general cases (see Table 49).
Case 1: Source port is peripheral; destination port is SARAM, DARAM, or
-
EMIF.
The channel waits for the synchronization event before reading from the
peripheral port into the channel FIFO (source synchronization). Once the
FIFO is filled, the DMA channel begins writing to the destination port to
empty the FIFO.
Case 2: Source port is SARAM, DARAM, or EMIF; destination is
-
peripheral.
As soon as the channel is enabled (EN = 1 in DMACCR), reads from the
source port are performed to load the channel FIFO. The FIFO writes to
the peripheral port do not begin until the synchronization event is detected
(destination synchronization). When the channel is operating in
frame-synchronization mode (FS = 1 in DMACCR), several prereads may
occur that might fill the FIFO while the channel is awaiting the
synchronization event.
Case 3: Source port is SARAM, DARAM, or EMIF; destination port is
-
SARAM, DARAM, or EMIF.
The channel waits for the synchronization event before reading from the
source port into the channel FIFO (source synchronization). Once the
FIFO is filled, the DMA channel begins writing to the destination port to
empty the FIFO.
Any port
Peripheral port
SARAM, DARAM or
EMIF port
SARAM, DARAM or
EMIF port
Destination Port
Any port
SARAM, DARAM or
EMIF port
Peripheral port
SARAM, DARAM or
EMIF port
DSP DMA
Synchronization
Event Triggers
No activity
Source read
Destination write
Source read
DSP Subsystem 143