MPC563XM Reference Manual, Rev. 1
Freescale Semiconductor
149
Preliminary—Subject to Change Without Notice
bwc[1:0]
Bandwidth control
This two-bit field provides a mechanism to effectively
throttle the amount of bus bandwidth consumed by
the DMA. In general, as the DMA processes the inner
minor loop, it continuously generates read/write,
read/write, ... sequences until the minor count is
exhausted. This field forces the DMA to stall after the
completion of each read/write access to control the
bus request bandwidth seen by the platform’s
cross-bar arbitration switch. To minimize start-up
latency, bandwidth control stalls are suppressed for
the first two AHB bus cycles and after the last write of
each minor loop.
The dynamic priority elevation setting elevates the
priority of the DMA as seen by the cross-bar
arbitration switch for the executing channel. Dynamic
priority elevation is suppressed during the first two
AHB bus cycles.
00 No dma_engine stalls
01 Dynamic priority elevation
10 dma_engine stalls for 4 cycles after each r/w
11 dma_engine stalls for 8 cycles after each r/w
major.linkch[5:0]
Link channel number
if (TCD.major.e_link = 0) then
No channel-to-channel linking (or chaining) is
performed after the outer "major" loop counter is
exhausted.
else
After the "major" loop counter is exhausted, the
dma_engine initiates a channel service request at
the channel defined by major.linkch[5:0] by setting
that channel’s TCD.start bit.
The value contained in major.linkch[5:0] must not
exceed the number of implemented channels.
done
Channel done
This flag indicates the DMA has completed the outer
major loop. It is set by the dma_engine as the citer
count reaches zero; it is cleared by software, or the
hardware when the channel is activated.
This bit must be cleared in order to write the
major.e_link or e_sg bits.
active
Channel active
This flag signals the channel is currently in execution.
It is set when channel service begins, and is cleared
by the dma_engine as the inner minor loop completes
or if any error condition is detected.
Name
Description
Value
Содержание MPC5632M
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