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CHAPTER 13 DMA FUNCTIONS
User’s Manual U15109EJ3V0UD
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(6) Start factor settings
The DMA start factor is set using bits 2 to 0 (DMAS2 to DMAS0) of the DMA start factor expansion register
(DMAS) in combination with bits 4 and 3 (TTYPn1, TTYPn0) of DMA channel control registers 0 to 5 (DCHC0 to
DCHC5)(n = 0 to 5).
Table 13-2 shows the DMA start factor settings.
Cautions 1. If the interrupt that is the DMA start factor is not masked, interrupt servicing is performed
each time DMA starts.
To prevent interrupt servicing from being performed, mask the interrupt.
2. If an interrupt source is generated asynchronously to the internal system clock, do not set
the interrupt source as a multiple DMA start trigger (for example, when the serial interface
is operated on the external clock input).
If set, the priority order of DMA may be reversed.