760
11054A–ATARM–27-Jul-11
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11054A–ATARM–27-Jul-11
SAM9X25
3.
Program TWI_IADR with b3 b4 b5 b6 b7 b8 b9 b10 (b10 is the LSB of the 10-bit
address)
below shows a byte write to an Atmel AT24LC512 EEPROM. This demonstrates
the use of internal addresses to access the device.
Figure 38-13.
Internal Address Usage
38.8.7
Using the DMA Controller (DMAC)
The use of the DMAC significantly reduces the CPU load.
To assure correct implementation, respect the following programming sequence.
1.
Initialize the DMAC (channels, memory pointers, size, etc.);
1.
Configure the master mode (DADR, CKDIV, etc.).
1.
Enable the DMAC.
1.
Wait for the DMAC flag.
1.
Disable the DMAC.
38.8.8
SMBUS Quick Command (Master Mode Only)
The TWI interface can perform a Quick Command:
1.
Configure the master mode (DADR, CKDIV, etc.).
2.
Write the MREAD bit in the TWI_MMR register at the value of the one-bit command to
be sent.
3.
Start the transfer by setting the QUICK bit in the TWI_CR.
Figure 38-14.
SMBUS Quick Command
38.8.9
Read-write Flowcharts
The following flowcharts shown in
,
,
and
give examples for
read and write operations. A polling or interrupt method can be used to check the status bits.
The interrupt method requires that the interrupt enable register (TWI_IER) be configured first.
S
T
A
R
T
M
S
B
Device
Address
0
L
S
B
R
/
W
A
C
K
M
S
B
W
R
I
T
E
A
C
K
A
C
K
L
S
B
A
C
K
FIRST
WORD ADDRESS
SECOND
WORD ADDRESS
DATA
S
T
O
P
TXCOMP
TXRDY
Write QUICK command in TWI_CR
TWD
A
S
DADR
R/W
P
Содержание SAM9X25
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