326
Chapter 8
DMA Controller (DMAC)
Preliminary User’s Manual U17566EE1V2UM00
Figure 8-2
Example of forcible interruption of DMA transfer
Caution
The resumed DMA transfer after NMI interruption cannot be executed with new
settings. New settings for a DMA transfer can be validated either after the end
of the current transfer or after the transfer has been forcibly terminated by
setting the INITn bit of the DCHCn register.
8.10 Forcible Termination
In addition to the forcible interruption operation by means of the NMI input,
DMA transfer can be forcibly terminated by the INITn bit of the DCHCn register.
The following is an example of the operation of a forcible termination.
Figure 8-3
shows a block transfer of channel 3 which begins during the DMA
block transfer of DMA channel 2. The block transfer of DMA channel 2 is
forcibly terminated by setting the INIT2 bit of its DCHC2 control register.
Figure 8-3
DMA transfer forcible termination example 1
DMA transfer stop
DMA transfer
DMA transfer
DMA transfer stop
EN0 bit of DCHC0 register
NMI (input)
Forcible
interruption
Forcible
interruption
Transfer
restart
DMA Transfer
Request CH2
DMA Transfer
Request CH3
CPU
DMA3
DMA3
DMA3 DMA3 CPU
CPU
CPU
CPU
CPU
DMA2
DMA2
DMA2
DMA2 DMA2
CPU
CPU
EN3 bit = 1
TC3 bit = 0
EN3 bit
0
TC3 bit
1
Set register
EN2 bit = 1
TC2 bit = 0
Set register
Set register
EN2 bit
0
TC2 bit = 0
DMA channel 3 terminal count
DMA channel 3 transfer begins
DMA channel 2 transfer is forcibly terminated
and the bus is released
DSAL2, DSAH2,
DDAL2, DDAH2
DSAL3, DSAH3,
DDAL3, DDAH3
DCHC2
(INIT2 bit = 1)
→
→
→
electronic components distributor