Synchronization: Triggering DMA Transfers
5-17
Direct Memory Access (DMA) Controller
5.6
Synchronization: Triggering DMA Transfers
Synchronization allows DMA transfers to be triggered by events such as inter-
rupts from internal peripherals or external pins. Three types of synchronization
can be enabled for each channel:
-
Read synchronization: Each read transfer waits for the selected event to
occur before proceeding.
-
Write synchronization: Each write transfer waits for the selected event to
occur before proceeding.
-
Frame synchronization: Each frame transfer waits for the selected event
to occur before proceeding.
Selection of Synchronization Events: The events are selected by the RSYNC
and WSYNC fields in the DMA channel primary control register. If FS = 1 in this
register, then the event selected by RSYNC enables an entire frame, and
WSNYC must be set to 00000b. If a channel is set up to operate in split mode
(SPLIT
0
00b), RSYNC and WSYNC must be set to non-zero values. Up to 31
events are available. If the value of these fields is set to 00000b, no synchroniza-
tion is necessary. In this case, the read, write, or frame transfers occur as soon
as the resource is available to that channel. The association between values in
these fields and events is shown in Table 5–6. This is similar to the fields in the
interrupt selector (see section 13.4,
Configuring the Interrupt Selector). The dif-
ferences are that the McBSP generates separate interrupts and DMA synchro-
nization events and that the DSPINT is located differently in the encoding.
Table 5–6. Synchronization Events
Event Number
(Binary)
Event Acronym
Event Description
00000
None
No synchronization
00001
TINT0
Timer 0 interrupt
00010
TINT1
Timer 1 interrupt
00011
SD_INT
EMIF SDRAM timer interrupt
00100
EXT_INT4
External interrupt pin 4
00101
EXT_INT5
External interrupt pin 5
00110
EXT_INT6
External interrupt pin 6
00111
EXT_INT7
External interrupt pin 7
01000
DMA_INT0
DMA channel 0 interrupt
01001
DMA_INT1
DMA channel 1 interrupt