150
MC95FG308 / MC95FG208
ABOV Semiconductor Co., Ltd.
11.9.7 Synchronization / Arbitration
Clock synchronization is performed using the wired-AND connection of I2C interfaces to the SCL line. This means that
a HIGH to LOW transition on the SCL line will cause the devices concerned to start counting off their LOW period and
it will hold the SCL line in that state until the clock HIGH state is reached. However the LOW to HIGH transition of this
clock may not change the state of the SCL line if another clock is still within its LOW period. In this way, a synchronized
SCL clock is generated with its LOW period determined by the device with the longest clock LOW period, and its HIGH
period determined by the one with the shortest clock HIGH period.
A master may start a transfer only if the bus is free. Two or more masters may generate a START condition. Arbitration
takes place on the SDA line, while the SCL line is at the HIGH level, in such a way that the master which transmits a
HIGH level, while another master is transmitting a LOW level will switch off its DATA output state because the level on
the bus doesn’t correspond to its own level. Arbitration continues for many bits until a winning master gets the
ownership of I2C bus. Its first stage is comparison of the address bits.
Figure 11.56
Clock Synchronization during Arbitration Procedure
Figure 11.57
Arbitration Procedure of Two Masters
Device1
DataOut
SCL on BUS
Device2
DataOut
SDA on BUS
S
Arbitration Process
not adaped
Device 1 loses
Arbitration
Device1 outputs
High
High Counter
Reset
Fast Device
SCLOUT
Slow Device
SCLOUT
SCL
Wait High
Counting
Start High
Counting
Содержание MC95FG208 Series
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Страница 23: ...23 MC95FG308 MC95FG208 ABOV Semiconductor Co Ltd Figure 4 10 16 Pin SOP Package...
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