14.3.8 Arbitration
If two or more master-transmitters attempt to start a transmission on the same bus at approximately the same
time, an arbitration procedure is invoked. The arbitration procedure uses the data presented on the serial data
bus (SDA) by the competing transmitters.
illustrates the arbitration procedure between two devices.
The first master-transmitter that releases the SDA line high is overruled by another master-transmitter that drives
the SDA low. The arbitration procedure gives priority to the device that transmits the serial data stream with
the lowest binary value. Should two or more devices send identical first bytes, arbitration continues on the
subsequent bytes.
If the I2C module is the losing master, it switches to the slave-receiver mode, sets the arbitration lost (ARBL)
flag, and generates the arbitration-lost interrupt request.
If during a serial transfer the arbitration procedure is still in progress when a repeated START condition or
a STOP condition is transmitted to SDA, the master-transmitters involved must send the repeated START
condition or the 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
1
0
0
0
1
0
0
0
1
1
1
1
1
0
Device #1 loses arbitration
and switches off
Bus line
SCL
Data from
device #1
Data from
device #2
Bus line
SDA
Device #2 drives SDA
Figure 14-15. Arbitration Procedure Between Two Master-Transmitters
Inter-Integrated Circuit Module (I2C)
848
TMS320x2806x Microcontrollers
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
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