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DMA Controller Module
MCF52235 ColdFire® Integrated Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor
20-15
DCR
n
[AA] equals 1, the BCR
n
may skip over the programmed boundary, in which case, the DMA bus
request is not negated.
If BWC equals 000, the request signal remains asserted until BCR
n
reaches zero. DMA has priority over
the core. In this scheme, the arbiter can always force the DMA to relinquish the bus.
20.4.5
Termination
An unsuccessful transfer can terminate for one of the following reasons:
•
Error conditions—When the DMA encounters a read or write cycle that terminates with an error
condition, DSR
n
[BES] is set for a read and DSR
n
[BED] is set for a write before the transfer is
halted. If the error occurred in a write cycle, data in the internal holding register is lost.
•
Interrupts—If DCR
n
[INT] is set, the DMA drives the appropriate internal interrupt signal. The
processor can read DSR
n
to determine whether the transfer terminated successfully or with an
error. DSR
n
[DONE] is then written with a one to clear the interrupt and the DONE and error bits.
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
United
States
prior
to
September
2010:MCF52234CVM60,
MCF52235CVM60