Motorola DSP56301 User Manual
Page 104
DMA Control Registers 5–0 (DCR[5–0])
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DSP56301 User’s Manual
22
DIE
0
DMA Interrupt Enable
Generates a DMA interrupt at the end of a DMA block transfer after the counter is loaded
with its preloaded value. A DMA interrupt is also generated when software explicitly clears
DE during a DMA operation. Once asserted, a DMA interrupt request can be cleared only by
the service of a DMA interrupt routine. To ensure that a new interrupt request is not
generated, clear DIE while the DMA interrupt is serviced and before a new DMA request is
generated at the end of a DMA block transfer—that is, at the beginning of the DMA channel
interrupt service routine. When DIE is cleared, the DMA interrupt is disabled.
21–19
DTM[2–0]
0
DMA Transfer Mode
Specify the operating modes of the DMA channel, as follows:
DTM[2–0]
Trigger
DE
Cleared
After
Transfer Mode
000
request
Yes
Block Transfer—DE enabled and DMA request initiated.
The transfer is complete when the counter decrements to
zero and the DMA controller reloads the counter with the
original value.
001
request
Yes
Word Transfer—A word-by-word block transfer (length
set by the counter) that is DE enabled. The transfer is
complete when the counter decrements to zero and the
DMA controller reloads the counter with the original
value.
010
request
Yes
Line Transfer—A line by line block transfer (length set by
the counter) that is DE enabled. The transfer is complete
when the counter decrements to zero and the DMA
controller reloads the counter with the original value.
011
DE
Yes
Block Transfer—The DE-initiated transfer is complete
when the counter decrements to zero and the DMA
controller reloads the counter with the original value.
100
request
No
Block Transfer—The transfer is enabled by DE and
initiated by the first DMA request. The transfer is
completed when the counter decrements to zero and
reloads itself with the original value. The DE bit is not
cleared at the end of the block, so the DMA channel waits
for a new request.
Note:
The DMA End-of-Block-Transfer Interrupt
cannot be used in this mode.
101
request
No
Word Transfer—The transfer is enabled by DE and
initiated by every DMA request. When the counter
decrements to zero, it is reloaded with its original value.
The DE bit is not automatically cleared, so the DMA
channel waits for a new request.
Note:
The DMA End-of-Block-Transfer Interrupt
cannot be used in this mode.
110–111
Reserved
Note:
When DTM[2–0] = 001 or 101, some peripherals can generate a second DMA request while the DMA controller is
still processing the first request (see the description of the DRS bits).
Table 4-12. DMA Control Register (DCR) Bit Definitions (Continued)
Bit
Number
Bit Name
Reset
Value
Description