MAX96708 datasheet(60/68 Pages) MAXIM

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Control-Channel Interfaces

I2C

Set I2CSEL = 1 to configure the control channel for

I2C-to-I2C mode. In this mode, the control channel

forwards I2C commands from the microcontroller side

to the other side of the GMSL link. The remote device

acts as an I2C master to the other peripherals connected

to the remote side device. I2C-to-I2C mode uses clock

stretching to hold the microcontroller until the data and

the acknowledge/no-acknowledge have been sent across

the link.

I2C Bit Rate

The I2C interface accepts bit rates from 9.6kbps to 1Mbps.

The local I2C rate is set by the microcontroller. The remote

I2C rate is set by the remote device. By default the control

channel is set up for a 400kbps-to-I2C bit rate. Program the

I2C_MSTBT and SLV_SH bits (register 0x0D) to match the

desired microcontroller I2C rate.

Software Programming of the Device Addresses

The serializer and deserializer have programmable device

addresses. This allows multiple GMSL devices, along with

I2C peripherals, to coexist on the same control channel.

The serializer device address is in register 0x00 of each

device, while the deserializer device address is in register

0x01 of each device. To change a device address, first

write to the device whose address changes (register 0x00

of the serializer for serializer device address change, or

address change). Then write the same address into the

corresponding register on the other device (register 0x00

of the deserializer for serializer device address change,

or register 0x01 of the serializer for deserializer device

address change).

I2C Address Translation

The device supports I2C address translation for up to

two device addresses. Use address translation to assign

unique device addresses to peripherals with limited

I2C addresses. Source addresses (address to translate

from) are stored in registers 0x09 and 0x0B. Destination

addresses (address to translate to) are stored in registers

0x0A and 0x0C.

Configuration Blocking

The device can block changes to its registers. Set

CFGBLOCK to make all registers read only. Once set, the

registers remain blocked until the supplies are removed or

until PWDNB is low.

Cascaded/Parallel Devices

GMSL supports cascaded and parallel devices connected

through I2C. When cascading or using parallel links,

all I2C commands are forwarded to all links. Each link

attempts to hold the control channel until it receives an

acknowledge/non-acknowledge from the remote side

device. It is important to keep the control channel active

between links in order to prevent timeout. If a link is

unused, keep the control channel clear by turning on the

configuration link, disconnecting the I2C lines, or power-

ing down the unused device.

Dual μC Control

Most systems use a single microcontroller; however, µCs

can reside on each side simultaneously and trade off

running the control channel. Contention occurs if both µCs

attempt to use the control channel at the same time. It is

up to the user to prevent this contention by implementing

a higher-level protocol. In addition, the control channel

does not provide arbitration between I2C masters on both

sides of the link. An acknowledge frame is not generated

when communication fails due to contention. If communi-

cation across the serial link is not required, the µCs can

disable the forward and reverse control channel using

the FWDCCEN and REVCCEN bits (0x04, D[1:0]) in the

serializer/deserializer. Communication across the serial link

is stopped and contention between µCs cannot occur.

www.maximintegrated.com

Maxim Integrated │ 60

MAX96708

14-Bit GMSL Deserializer

with Coax or STP Cable Input

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