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Chapter 7
DMA Functions (DMA Controller)
Preliminary User’s Manual U15839EE1V0UM00
7.10 Forcible
Interruption
DMA transfer can be forcibly interrupted by NMI input during DMA transfer. At such a time, the DMAC
clears the ENn bit of the DCHCn register of all channels and the DMA transfer disabled state is entered.
An NMI request can then be acknowledged after the DMA transfer executed during NMI input is termi-
nated.
In the single-step transfer mode, block transfer mode or line transfer mode the DMA transfer request is
held in the DMAC. If the ENn bit is set the DMA transfer restarts from the point where it was interrupted.
In the single transfer mode, if the ENn bit is set, the next DMA transfer request is acknowledged and
DMA transfer begins.
Figure 7-27:
Example of Forcible Interruption of DMA Transfer
Caution:
To forcibly interrupt DMA transfer and stop the next transfer from occurring, the NMI
signal must be made active before the end of the DMA transfer currently under exe-
cution. Moreover, although it is possible to restart DMA transfer following an inter-
ruption, this transfer cannot be executed under new settings (new conditions).
Execute DMA transfer under new settings either after the end of the current transfer
or after transfer has been forcibly terminated by setting the INITn bit of the DCHCn
register.
Remark:
n = 0 to 3
DMA transfer stop
DMA transfer
DMA transfer
DMA transfer stop
01H
DRST register
EN0 bit of DCHC0 register
DDIS register
NMI (input)
01H
Forcible
interruption
Forcible
interruption
Transfer
restart
Содержание mPD703128
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