CHAPTER 6 DMA FUNCTIONS (DMA CONTROLLER)
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User’s Manual U14359EJ4V0UM
6.10 DMA Transfer Start Factors
There are 3 types of DMA transfer start factors, as shown below.
(1) Request from an external pin (DMARQn)
Requests from the DMARQn pin are sampled each time the CLKOUT signal rises (n = 0 to 3).
Hold the request from DMARQn pin until the corresponding DMAAKn signal becomes active.
If a state whereby the Enn bit of the DCHCn register = 1 and the TCn bit = 0 is set, the DMARQn signal in the
TI state becomes valid. If the DMARQn signal becomes active in the TI state, it changes to the T0 state and
DMA transfer is started.
(2) Request from software
If the STGn, Enn, and TCn bits of the DCHCn register are set as follows, DMA transfer starts (n = 0 to 3).
•
STGn bit = 1
•
Enn bit = 1
•
TCn bit = 0
(3) Request from on-chip peripheral I/O
If, when the Enn and TCn bits of the DCHCn register are set as shown below, an interrupt request is issued
from the on-chip peripheral I/O that is set in the DTFRn register, DMA transfer starts (n = 0 to 3).
•
Enn bit = 1
•
TCn bit = 0
Remark
Since the DMARQn signal is level-sampled and not edge-detected, to enable edge detection of a DMA
request, set an external interrupt request for the DMA start trigger instead of using the DMARQn signal
(n = 0 to 3).
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