Datasheet

1
0 0 0
1
0 0 0
1 1
111
n
Device 1 Lost Arbitration
and Switches Off
Bus Line
SCL
Data From
Device 1
Data From
Device 2
Bus Line
SDA
Master Transmitter
S
A A
P
1) UCTR=1 (Transmitter)
2) UCTXSTT=1
Successful
transmission to a
slave receiver
UCBxTXIFG=1
UCBxTXIFG=1
DATADATA
A A
UCTXSTP=1
UCTXSTT=0 UCTXSTP=0
11110 xx/W SLA (2.)
S
A
P
1) UCTR=0 (Receiver)
2) UCTXSTT=1
Successful
reception from a
slave transmitter
DATADATA
A
UCTXSTP=1
A
UCTXSTT=0 UCTXSTP=0
A A
11110 xx/W SLA (2.) 11110 xx/R
Master Receiver
S
UCBxRXIFG=1
www.ti.com USCI Operation: I
2
C Mode
17.3.4.2.3 I
2
C Master 10-Bit Addressing Mode
The 10-bit addressing mode is selected when UCSLA10 = 1 and is shown in Figure 17-14.
Figure 17-14. I
2
C Master 10-bit Addressing Mode
17.3.4.2.4 Arbitration
If two or more master transmitters simultaneously start a transmission on the bus, an arbitration procedure
is invoked. Figure 17-15 shows the arbitration procedure between two devices. The arbitration procedure
uses the data presented on SDA by the competing transmitters. The first master transmitter that generates
a logic high is overruled by the opposing master generating a logic low. The arbitration procedure gives
priority to the device that transmits the serial data stream with the lowest binary value. The master
transmitter that lost arbitration switches to the slave receiver mode, and sets the arbitration lost flag
UCALIFG. If two or more devices send identical first bytes, arbitration continues on the subsequent bytes.
Figure 17-15. Arbitration Procedure Between Two Master Transmitters
If the arbitration procedure is in progress when a repeated START condition or STOP condition is
transmitted on SDA, the master transmitters involved in arbitration must send the repeated START
condition or STOP condition at the same position in the format frame. Arbitration is not allowed between:
• A repeated START condition and a data bit
• A STOP condition and a data bit
• A repeated START condition and a STOP condition
463
SLAU144J–December 2004–Revised July 2013
Universal Serial Communication Interface, I
2
C Mode
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