DS32EL0421, DS32ELX0421

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SNLS282F – MAY 2008 – REVISED APRIL 2013

Register Recipes

Many features of the serializer contained within the SMBus registers require multiple writes to configure and

enable. This methodology was implemented to prevent accidental register writes from causing undesired device

behavior. Several recipes for common features are listed below. When experimenting with other SMBus register

features, be sure to read through the register map for override and enable bits.

SCRAMBLER OVERRIDE CONTROL

The scrambler’s default settings are described in the DEVICE CONFIGURATION section. However, the

scrambler’s setting can be overridden if desired.

Reg 22’h, write 08’h

Reg 21’h, write to bit 3 to enable/disable

75

Ω MODE

The serializer can be programmed to interface with 75

Ω media by using the recipe shown below. The inverting

serial output should be terminated when interfacing with single ended media.

Reg 2F’h, write 0 to bit 5

OUTPUT CHANNEL MUX CONTROL

DS32ELX0421 only. TxOUT0 is the output channel enabled by default. By using the external pin TxOUT1_EN,

TxOUT1 will be activated along with TxOUT0. If an application requires that only one channel be active at a time,

the following recipe allows for each channel to be enabled or disabled independent of the other.

Reg 2F’h, write 1’b to bit 2

Reg 2F’h, write to bits 1 or 0 to control the output channels

OUTPUT THE SERIAL CLOCK ON GPIO2

It is very helpful to be able to monitor high speed communication systems and observe their signal integrity.

Generally, this is done with a high speed real time oscilloscope or a sampling oscilloscope. Sampling

oscilloscopes require a reference clock to trigger on. The following recipe can be used to bring out the serial

clock on GPIO2 to provide a trigger for sampling oscilloscopes.

Reg 04’h, write 21’h

Power Save Mode

When a system does not need to transmit high speed data from the DS32EL0421 or DS32ELX0421, the power

consumption of the device can be managed as described in the POWER MANAGEMENT section on the

Functional Description page. The following recipe powers down many of the analog and digital blocks in the

serializer, but leaves the SMBus module operational. Please note that in order to resume normal operation the

recipe below will have to be unwritten.

Reg 01'h, write 10'h

Reg 26'h, write 40'h

Redundancy / Fail Over Configuration

DS32ELX0421 only. Implementing a redundancy system with the DS32ELX0421 can be done in several ways.

One method would be to program the redundancy or fail over logic into the host device or FPGA. The recipe

below will describe a different method, for which a DS32ELX0421 will communicate to two different DS32EL0124

deserializers. The recipe below will configure the DS32ELX0421 serializer to automatically switch to the alternate

output when the current high speed link fails.

Configure all device with Remote Sense enabled either by pin or register control. Pull TxOUT1_EN pin high

reg 2F'h, write 2D'h

Reg 2F'h, write 28'h

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Product Folder Links: DS32EL0421 DS32ELX0421