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DMA Interface
8-10
MC68322 USER’S MANUAL
MOTOROLA
8.7.2 Bad Address Termination
If at some point during the DMA transfer an address supplied by the DMA to the DRAM or
MC68322 bus interfaces is incorrect (not mapped to a valid bank), an address fault occurs.
The DMA transfer terminates, the ILA bit in the channel’s interrupt event register is set, and
an interrupt is posted to the core if enabled. As a result of this bad address error, the DMA
channel will park in an error condition. The DMA channel must then be reset using one of
soft-reset register’s DMA bits before a new operation can be initiated. A write to either the
GDR or PDR bits in the soft-reset register will initiate a DMA soft-reset operation. See
Section 5 Interrupt and Exception Handling for more information. During the reset
condition, only the DMA channel control logic is affected. Initial register values are not
cleared.
8.7.3 Core-Forced Termination
If, during a DMA transfer, the core sets the FR bit in the channel’s configuration register, the
DMA controller will terminate any ongoing transfer for that channel. If the DMA channel is
receiving data from the MC68322 bus or the PPI, any data remaining in the internal data
latch is written to DRAM. If the DMA channel is sending data to the MC68322 bus, any data
remaining in the data latch is discarded. When the data transfers are complete, the channel
shuts down, sets the CMP bit in the channel’s interrupt event register, and returns to the idle
state. Depending on the value remaining in the transfer counters, it is possible to set the FR
bit in the channel’s configuration register, and still have the DMA transfer terminate normally
due to the transfer counters decrementing to zero. If this condition occurs, both the CMP and
TCR bits will be set in the channel’s interrupt event register.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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