Datasheet

MAX9273
22-Bit GMSL Serializer with Coax or
STP Cable Drive
27Maxim Integrated
I
2
C Interface
In I
2
C-to-I
2
C mode, the serializer control-channel inter-
face sends and receives data through an I
2
C-compatible
2-wire interface. The interface uses a serial-data line
(SDA) and a serial-clock line (SCL) to achieve bidirec-
tional communication between master and slave(s). A FC
master initiates all data transfers to and from the device
and generates the SCL clock that synchronizes the data
transfer. When an I
2
C transaction starts on the local-side
device’s control-channel port, the remote-side device’s
control-channel port becomes an I
2
C master that inter-
faces with remote-side I
2
C peripherals. The I
2
C master
must accept clock stretching that is imposed by the seri-
alizer (holding SCL low). The SDA and SCL lines operate
as both an input and an open-drain output. Pullup resis-
tors are required on SDA and SCL. Each transmission
consists of a START condition (Figure 6) sent by a mas-
ter, followed by the device’s 7-bit slave address plus a
R/W bit, a register address byte, one or more data bytes,
and finally a STOP condition.
START and STOP Conditions
Both SCL and SDA remain high when the interface is not
busy. A master signals the beginning of a transmission
with a START (S) condition by transitioning SDA from high
to low while SCL is high (Figure 24). When the master has
finished communicating with the slave, it issues a STOP
(P) condition by transitioning SDA from low to high while
SCL is high. The bus is then free for another transmission.
Bit Transfer
One data bit is transferred during each clock pulse
(Figure 25). The data on SDA must remain stable while
SCL is high.
Acknowledge
The acknowledge bit is a clocked 9th bit that the recipient
uses to handshake receipt of each byte of data (Figure 26).
Thus, each byte transferred effectively requires nine bits.
The master generates the 9th clock pulse, and the recipi-
ent pulls down SDA during the acknowledge clock pulse.
The SDA line is stable low during the high period of the
clock pulse. When the master is transmitting to the slave
device, the slave device generates the acknowledge bit
Figure 23. Format Conversion Between GMSL UART and I
2
C with Register Address (I2CMETHOD = 1)
: MASTER TO SLAVE
SERIALIZER/DESERIALIZER
SERIALIZER/DESERIALIZER
SERIALIZER/DESERIALIZER
UART-TO-I
2
C CONVERSION OF READ PACKET (I2CMETHOD = 1)
UART-TO-I
2
C CONVERSION OF WRITE PACKET (I2CMETHOD = 1)
FC
SERIALIZER/DESERIALIZERFC
SYNC FRAME
11 11 11 11 11 11 11
1111 11 11 11 11 11
DEVICE ID + RD REGISTER ADDRESS NUMBER OF BYTES
SYNC FRAME DEVICE ID + WR REGISTER ADDRESS NUMBER OF BYTES DATA 0DATA NACK FRAME
ACK FRAME DATA
0D
ATA N
DATA NADATA 0WADEV IDS AP
PERIPHERAL
PERIPHERAL
S
1118
8811117 11
8
1117
DEV ID RA AAPDATA 0DATA N
: SLAVE TO MASTER S: START P: STOP A: ACKNOWLEDGE