Rainbow Electronics MAX5945 User 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