R01UH0092EJ0110 Rev.1.10
Page 248 of 807
Jul 31, 2012
M16C/64C Group
16. DMAC
16.3.6
Repeat Transfer Mode
In repeat transfer mode, when the DMAi transfer counter underflows, it is reloaded with the value of the
DMAi transfer counter reload register and DMA transfer continues. Figure 16.4 shows an Operation
Example in Repeat Transfer Mode.
Figure 16.4
Operation Example in Repeat Transfer Mode
DMA
CPU
DMA
CPU
DMA
CPU
Bus
Undefined
02h
01h
00h
When a transfer begins, the DMAS bit becomes 0.
Underflow
Set to 0 by an interrupt request acknowledgement
or by a program.
Set to 1 by a program.
Repeat Transfer Mode
DMAS bit
TCRi register
IR bit
DMAE bit
i = 0 to 3
DMAS, DMAE: Bits in the DMiCON register
IR: Bit in the DMiIC register
The above assumes the following:
The TCRi register value is 02h (there are three transfers).
02h
CPU
DMA
01h
CPU
Reload
Summary of Contents for M16C Series
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