Datasheet
SAM9G20
DS60001516A-page 414 2017 Microchip Technology Inc.
Figure 30-11: Master Write with One, Two or Three Bytes Internal Address and One Data Byte
Figure 30-12: Master Read with One, Two or Three Bytes Internal Address and One Data Byte
• 10-bit Slave Addressing
For a slave address higher than 7 bits, the user must configure the address size (IADRSZ) and set the other slave address bits in the
internal address register (TWI_IADR). The two remaining Internal address bytes, IADR[15:8] and IADR[23:16] can be used the same as
in 7-bit Slave Addressing.
Example:
Address a 10-bit device (10-bit device address is b1 b2 b3 b4 b5 b6 b7 b8 b9 b10)
1. Program IADRSZ = 1,
2. Program DADR with 1 1 1 1 0 b1 b2 (b1 is the MSB of the 10-bit address, b2, etc.)
3. Program TWI_IADR with b3 b4 b5 b6 b7 b8 b9 b10 (b10 is the LSB of the 10-bit address)
Figure 30-13 below shows a byte write to a Microchip AT24LC512 EEPROM. This demonstrates the use of internal addresses to access
the device.
Figure 30-13: Internal Address Usage
30.6.3.7 Using the Peripheral DMA Controller (PDC)
The use of the PDC significantly reduces the CPU load.
To assure correct implementation, respect the following programming sequences:
• Data Transmit with the PDC
1. Initialize the transmit PDC (memory pointers, size, etc.).
2. Configure the master mode (DADR, CKDIV, etc.).
3. Start the transfer by setting the PDC TXTEN bit.
4. Wait for the PDC end TX flag.
5. Disable the PDC by setting the PDC TXDIS bit.
S DADR W A IADR(23:16) A IADR(15:8) A IADR(7:0) A DATA A P
S DADR W A IADR(15:8) A IADR(7:0) A P
DATA A
A IADR(7:0) A P
DATA AS DADR W
TWD
Three bytes internal address
Two bytes internal address
One byte internal address
TWD
TWD
S DADR
W
A IADR(23:16) A
IADR(15:8)
A
IADR(7:0) A
S DADR W A IADR(15:8)
A IADR(7:0) A
A
IADR(7:0) A
S DADR W
DATA N P
Sr DADR R A
Sr DADR R A DATA N P
Sr
DADR
RA DATA NP
TWD
TWD
TWD
Three bytes internal address
Two bytes internal address
One byte internal address
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