AT32UC3L064_1 ATMEL [ATMEL Corporation], AT32UC3L064_1 Datasheet - Page 493

• Manufacturer Part Number: AT32UC3L064_1
• Description: AVR32 32-bit Microcontroller
• Manufacturer: ATMEL [ATMEL Corporation]

Figure 22-11. Arbitration Cases
22.8.7
22.8.7.1
32099A–AVR32–06/09
Data from a Master
TWI DATA transfer
Data from TWI
(DADR + W + START + Write THR)
Combined Transfers
ARBLST
A transfer is programmed
TWCK
Write Followed by Write
TWD
TWCK
TWD
CMDR and NCMDR may be used to generate longer sequences of connected transfers, since
generation of START and/or STOP conditions is programmable on a per-command basis.
Programming NCMDR with START=1 when the previous transfer was programmed with
STOP=0 will cause a REPEATED START on the bus. The ability to generate such connected
transfers allows arbitrary transfer lengths, since it is legal to program CMDR with both
START=0 and STOP=0. If this is done in master receiver mode, the CMDR.ACKLAST bit must
also be controlled.
As for single data transfers, the TXRDY and RXRDY bits in the Status Register indicates when
data to transmit can be written to the THR, or when received data can be read from RHR.
Transfer of data to THR and from RHR can also be done automatically by DMA, see
the Peripheral DMA Controller” on page 491
Consider the following transfer:
START, DADR+W, DATA+A, DATA+A, REPSTART, DADR+W, DATA+A, DATA+A, STOP.
To generate this transfer:
1. Program CMDR with START=1, STOP=0, DADR, NBYTES=2 and READ=0.
2. Program NCMDR with START=1, STOP=1, DADR, NBYTES=2 and READ=0.
3. Wait until SR.TXRDY==1, then write first data byte to transfer to THR.
4. Wait until SR.TXRDY==1, then write second data byte to transfer to THR.
S
S
S
1
1
1
Transfer is stopped
0 0
0
0 0
1
1 1
1 1
TWI stops sending data
Arbitration is lost
(DADR + W + START + Write THR)
Transfer is programmed again
Data from the master
Bus is busy
Transfer is kept
P
P
Bus is free
Bus is considered as free
Transfer is initiated
S
S
S
1
1
1
0
0 0
0
1
0
1 1
The master stops sending data
1 1
Arbitration is lost
AT32UC3L
Data from the TWI
“Using
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