Rainbow Electronics MAX7470 - Manual (Page 10)

MAX7469/MAX7470
HDTV Continuously Variable
Anti-Aliasing Filters
10 _______________________________________________________________________________________
START and STOP Conditions
A master device initiates communication by issuing a
START condition, a high-to-low transition on SDA with SCL
high (Figure 2). The master terminates transmission by a
STOP condition (see the
Acknowledge Bit (ACK) and Not-
Acknowledge Bit (NACK) section). A STOP condition is a
low-to-high transition on SDA while SCL is high (Figure 2).
The STOP condition frees the bus. If a repeated START
condition is generated instead of a STOP condition, the
bus remains active. When a STOP condition or incorrect
address is detected, the MAX7469/
MAX7470 then ignore all communication on the I
2 C bus
until the next START or REPEATED START condition,
minimizing digital noise and feedthrough.
Early STOP Conditions
The MAX7469/MAX7470 recognize a STOP condition at
any point during transmission except when a STOP
condition occurs in the same high pulse as a START
condition (Figure 3). This condition is not a legal I
2 C for-
mat; at least one clock pulse must separate any START
and STOP conditions. The MAX7469/MAX7470 discard
any data received during a data transfer aborted by an
early STOP condition.
Repeated START (S r ) Conditions
An Sr condition is used to indicate a change in direc-
tion of data flow (see the
Read Cycle section). Sr can
also be used when the bus master is writing to several
I
2 C devices and does not want to relinquish control of
the bus. The MAX7469/MAX7470 serial interface sup-
ports continuous write operations with (or without) an Sr
condition separating them.
START START STOP ILLEGAL STOP
LEGAL STOP CONDITION ILLEGAL STOP CONDITION
SCL
SDA
SCL
SDA
Figure 3. Early STOP Conditions
SCL
SDA
S S r P
Figure 2. START/STOP Conditions