Rainbow Electronics MAX5945 - Manual (Page 19)

Start and Stop Conditions
Both SCL and SDA remain high when the interface is
not busy. A master signals the beginning of a transmis-
sion with a START (S) condition by transitioning SDA
from high to low while SCL is high. When the master fin-
ishes communicating with the slave, the master issues
a STOP (P) condition by transitioning SDA from low to
high while SCL is high. The stop condition frees the bus
for another transmission.
MAX5945
Quad Network Power Controller
for Power-Over-LAN
______________________________________________________________________________________ 19
Figure 5. 2-Wire Serial Interface Timing Details
SCL
SDAIN
t LOW
t HIGH
t R t F
t BUF
START
CONDITION
STOP
CONDITION
REPEATED START CONDITION START CONDITION
t HD, STA
t SU, DAT
t HD, DAT
t SU, STA
t HD, STA
t SU, STO
Figure 6. 3-Wire Serial Interface Timing Details
SCL
SDAIN/SDA
t LOW
t HIGH
t R t F
t BUF
START
CONDITION
STOP
CONDITION
REPEATED START CONDITION START CONDITION
t HD, STA
t SU, DAT
t HD, DAT
t SU, STA
t HD, STA
t SU, STO
Figure 8. Bit Transfer
SDA
SCL
DATA LINE STABLE;
DATA VALID
.
CHANGE OF
DATA ALLOWED
Figure 7. Start and Stop Conditions
START STOP
S P
SDA/
SDAIN
SCL