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Slave Transmitter
Slave Receiver
2.6.1
Arbitration
SPRU760B
This mode can be entered only from the slave receiver mode. With any of the
address formats (Figure 21 (a), (b), and (c)), the slave transmitter is entered
if the slave address byte is the same as its own address and bit R/W_ has been
transmitted, if R/W_ is high. The slave transmitter shifts the serial data out on
the data line SDA in synch with the clock pulses that are generated by the
master device. It does not generate the clock, but it can hold clock line SCL
low while the local host is required to intervene (XUDF).
In this mode, serial data bits received on the bus line SDA are shifted-in in
synch with the clock pulses on SCL that are generated by the master device.
It does not generate the clock, but it can hold the clock line SCL low while the
local host is required to intervene (ROVR) following the reception of a byte.
If two or more master transmitters start a transmission on the same bus almost
simultaneously, an arbitration procedure is invoked. The arbitration procedure
uses the data presented on the serial bus by the competing transmitters. When
a transmitter senses that a high signal it has presented on the bus has been
overruled by a low signal, it switches to the slave receiver mode, sets the
arbitration lost (AL) flag, and generates the arbitration lost interrupt. Figure 22
shows the arbitration procedure between two devices. 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.
I2C Multimaster Peripheral
Serial Interfaces
63
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