Atmel SAM4L Xplained Pro Evaluation Kit Atmel ATSAM4L-XPRO ATSAM4L-XPRO Data Sheet
Product codes
ATSAM4L-XPRO
714
42023E–SAM–07/2013
ATSAM4L8/L4/L2
Figure 27-8. Master Read with One Data Byte
Figure 27-9. Master Read with Multiple Data Bytes
27.8.5
Using the Peripheral DMA Controller
The use of the Peripheral DMA Controller significantly reduces the CPU load. The user can set
up ring buffers for the Peripheral DMA Controller, containing data to transmit or free buffer space
to place received data.
up ring buffers for the Peripheral DMA Controller, containing data to transmit or free buffer space
to place received data.
To assure correct behavior, respect the following programming sequences:
27.8.5.1
Data Transmit with the Peripheral DMA Controller
1.
Initialize the transmit Peripheral DMA Controller (memory pointers, size, etc.).
2.
Configure the TWIM (ADR, NBYTES, etc.).
3.
Start the transfer by enabling the Peripheral DMA Controller to transmit.
4.
Wait for the Peripheral DMA Controller end-of-transmit flag.
5.
Disable the Peripheral DMA Controller.
27.8.5.2
Data Receive with the Peripheral DMA Controller
1.
Initialize the receive Peripheral DMA Controller (memory pointers, size, etc.).
2.
Configure the TWIM (ADR, NBYTES, etc.).
3.
Start the transfer by enabling the Peripheral DMA Controller to receive.
4.
Wait for the Peripheral DMA Controller end-of-receive flag.
5.
Disable the Peripheral DMA Controller.
TWD
SR.IDLE
RXRDY
Write START &
STOP bit
NBYTES set to 1
Read RHR
S
DADR
R
A
DATA
N
P
TWD
SR.IDLE
RXRDY
Write START +
STOP bit
NBYTES set to m
S
DADR
R
A
DATAn
A
DATAn+m-1
A
N
DATAn+m
P
Read RHR
DATAn
DATAn+1
Read RHR
DATAn+m-2
Read RHR
DATAn+m-1
Read RHR
DATAn+m
Send STOP
When NBYTES=0