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14.3.6
Ending DMA Transfer
The conditions for ending DMA transfer are different for ending on individual channels and for
ending on all channels together. Except for the case where transfer ends when the value in the
DMA transfer count register (DMATCR) reaches 0, the following conditions apply to ending
transfer.
1. Cycle Steal Mode (External Request, On-Chip Peripheral Module Request, Auto-Request)
When a transfer end condition is satisfied, acceptance of DMAC transfer requests is
suspended. The DMAC completes transfer for the transfer requests accepted up to the point at
which the transfer end condition was satisfied, then stops.
In cycle steal mode, the operation is the same for both edge and level transfer request
detection.
2. Burst Mode, Edge Detection (External Request, On-Chip Peripheral Module Request, Auto-
Request)
The delay between the point at which a transfer end condition is satisfied and the point at
which the DMAC actually stops is the same as in cycle steal mode. In burst mode with edge
detection, only the first transfer request activates the DMAC, but the timing of stop request
(DE = 0 in CHCR, DME = 0 in DMAOR) sampling is the same as the transfer request
sampling timing shown in 4 and 5 under Operation in section 14.3.5. Therefore, a transfer
request is regarded as having been issued until a stop request is detected, and the
corresponding processing is executed before the DMAC stops.
3. Burst Mode, Level Detection (External Request)
The delay between the point at which a transfer end condition is satisfied and the point at
which the DMAC actually stops is the same as in cycle steal mode. As in the case of burst
mode with edge detection, the timing of stop request (DE = 0 in CHCR, DME = 0 in DMAOR)
sampling is the same as the transfer request sampling timing shown in 2 and 3 under Operation
in section 14.3.5. Therefore, a transfer request is regarded as having been issued until a stop
request is detected, and the corresponding processing is executed before the DMAC stops.
4. Transfer Suspension Bus Timing
Transfer suspension is executed on completion of processing for one transfer unit. In dual
address mode transfer, write cycle processing is executed even if a transfer end condition is
satisfied during the read cycle, and the transfers covered in 1, 2, and 3 above are also executed
before operation is suspended.
Rev. 4.0, 04/00, page 470 of 850
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