Rainbow Electronics ATmega128L - Manual (Page 195)

195
ATmega128(L)
2467B–09/01
Figure 92. Arbitration Between two Masters
Note that arbitration is not allowed between:
• A REPEATED START condition and a data bit
• A STOP condition and a data bit
• A REPEATED START and a STOP condition
It is the user software’s responsibility to ensure that these illegal arbitration conditions
never occur. This implies that in multi-master systems, all data transfers must use the
same composition of SLA+R/W and data packets. In other words: All transmissions
must contain the same number of data packets, otherwise the result of the arbitration is
undefined.
SDA from
master A
SDA from
master B
SDA line
Synchronized
SCL line
START
Master A loses
arbitration, SDA
A
SDA