If at least one circular buffer is enabled, the DMA overflow request is conditioned to the start of ramp A
with an effective DMA transfer on previous ramp B (DMA acknowledge).
The update of all circular buffer values for ramp A can be done through a DMA channel triggered on a MC
trigger. The update of all circular buffer values for ramp B, can be done through a second DMA channel
triggered by the overflow DMA request.
Figure 36-36. DMA Triggers in RAMP and RAMP2 Operation Mode and Circular Buffer Enabled
"update"
ZERO
DMA Channel i
DMA Channel j
Update ramp A
Update ramp B
N-2
N-1
N
A
B
A
A
B
B
COUNT
Cycle
STATUS.IDX
DMA_CCx_req
DMA_OVF_req
Ramp
DMA Operation with Circular Buffer in DSBOTH Mode
When a CC channel is selected as a circular buffer, the related DMA request is not set on a compare
match detection, but on start of down-counting phase.
If at least one circular buffer is enabled, the DMA overflow request is conditioned to the start of up-
counting phase with an effective DMA transfer on previous down-counting phase (DMA acknowledge).
When up-counting, all circular buffer values can be updated through a DMA channel triggered by MC
trigger. When down-counting, all circular buffer values can be updated through a second DMA channel,
triggered by the OVF DMA request.
Figure 36-37. DMA Triggers in DSBOTH Operation Mode and Circular Buffer Enabled
COUNT
Cycle
CTRLB.DIR
DMA_CCx_req
DMA_OVF_req
Old Parameter Set
New Parameter Set
"update"
ZERO
DMA Channel i
DMA Channel j
Update Rising
Update Rising
N-2
N-1
N
Atmel SAM L22G / L22J / L22N [DATASHEET]
Atmel-42402E-SAM L22G / L22J / L22N_Datasheet_Complete-07/2016
827