SAM9M10_14 Datasheet, PDF (961/1385 Pages) ATMEL Corporation – Atmel | SMART ARM-based Embedded MPU

40.4.5 Programming a Channel
Four registers, the DMAC_DSCRx, the DMAC_CTRLAx, the DMAC_CTRLBx and DMAC_CFGx, need to be
programmed to set up whether single or multi-buffer transfers take place, and which type of multi-buffer transfer is
used. The different transfer types are shown in Table 40-2 on page 959.
The “BTSIZE, SADDR and DADDR” columns indicate where the values of DMAC_SARx, DMAC_DARx,
DMAC_CTLx, and DMAC_LLPx are obtained for the next buffer transfer when multi-buffer DMAC transfers are
enabled.
40.4.5.1 Programming Examples
40.4.5.2 Single-buffer Transfer (Row 1)
1. Read the Channel Handler Status Register DMAC_CHSR.ENABLE Field to choose a free (disabled)
channel.
2. Clear any pending interrupts on the channel from the previous DMAC transfer by reading the interrupt status
register, DMAC_EBCISR.
3. Program the following channel registers:
a. Write the starting source address in the DMAC_SADDRx register for channel x.
b. Write the starting destination address in the DMAC_DADDRx register for channel x.
c. Program DMAC_CTRLAx, DMAC_CTRLBx and DMAC_CFGx according to Row 1 as shown in Table
40-2 on page 959. Program the DMAC_CTRLBx register with both DST_DSCR and SRC_DSCR
fields set to one and AUTO field set to 0.
d. Write the control information for the DMAC transfer in the DMAC_CTRLAx and DMAC_CTRLBx reg-
isters for channel x. For example, in the register, you can program the following:
̶ i. Set up the transfer type (memory or non-memory peripheral for source and destination) and flow
control device by programming the FC of the DMAC_CTRLBx register.
̶ ii. Set up the transfer characteristics, such as:
– Transfer width for the source in the SRC_WIDTH field.
– Transfer width for the destination in the DST_WIDTH field.
– Source AHB Master interface layer in the SIF field where source resides.
– Destination AHB Master Interface layer in the DIF field where destination resides.
– Incrementing/decrementing or fixed address for source in SRC_INC field.
– Incrementing/decrementing or fixed address for destination in DST_INC field.
e. Write the channel configuration information into the DMAC_CFGx register for channel x.
̶ i. Designate the handshaking interface type (hardware or software) for the source and destination
peripherals. This is not required for memory. This step requires programming the
SRC_H2SEL/DST_H2SEL bits, respectively. Writing a ‘1’ activates the hardware handshaking
interface to handle source/destination requests. Writing a ‘0’ activates the software handshaking
interface to handle source/destination requests.
̶ ii. If the hardware handshaking interface is activated for the source or destination peripheral, assign a
handshaking interface to the source and destination peripheral. This requires programming the
SRC_PER and DST_PER bits, respectively.
f. If source picture-in-picture mode is enabled (DMAC_CTRLBx.SRC_PIP is enabled), program the
DMAC_SPIPx register for channel x.
g. If destination picture-in-picture mode is enabled (DMAC_CTRLBx.DST_PIP is enabled), program the
DMAC_DPIPx register for channel x.
4. After the DMAC selected channel has been programmed, enable the channel by writing a ‘1’ to the
DMAC_CHER.ENABLE[n] bit, where n is the channel number. Make sure that bit 0 of DMAC_EN.ENABLE
register is enabled.
SAM9M10 [DATASHEET]
Atmel-6355G-ATARM-SAM9M10-Datasheet_02-Sept-14
961