GS2985 datasheet(27/45 Pages) SEMTECH

27 / 45 page

GS2985 Multi-Rate SDI Reclocker with Equalization &

De-emphasis

Data Sheet

36663 - 5

July 2012

27 of 45

Proprietary & Confidential

When the DATA/CLOCK pin is set HIGH, the DDO1/RCO pin will output a copy of the

serial digital output.

When the DATA/CLOCK pin is set LOW, the DDO1/RCO pin will output a copy of the

recovered clock signal.

4.15 Host Interface

4.15.1 Introduction

The GS2985 offers a Serial Peripheral Interface (SPI) to access advanced features and

programmability. The polarity of the HIF pin tells the GS2985 whether or not the host

interface is active (HIF = 0) or in legacy mode (HIF = 1).

Using the host interface, it is possible to override the control pin settings, and such

settings will persist until the device has been powered-down and/or reset. The host

interface is capable of reading hard-wired pin configuration, pin override settings and

the values of all status monitoring pins.

There is an optional 3-state feature available in the Control Status Registers (CSR) that

puts the SPI SDO to high-impedance when it’s not being used (Register: TOP_1, Bit: 2).

The maximum operating speed of the SPI is 10MHz.

4.15.2 Legacy Mode & Start-up

In legacy mode, basic configuration of the device (including a subset of equalizer and

de-emphasis settings) are available at the pin level. In this mode, register settings are

automatically set to default so that the GS2985 is live at power-up.

4.15.3 Host Interface Mode & Start-up

In host interface mode, the user gains access to Control and Status Registers (CSRs) that

manage advanced features. In this mode, equalizer and de-emphasis settings are set

through the CSR.

The SPI control port is functional at start-up without the need for a separate, external

reset signal. However, all internal registers must be set to their default state by issuing a

required Reset Command via the SPI.

Table 4-10: Configuration of GS2985 Output Drivers and Mute/Disable Pins

DATA_MUTE

DDO1_DISABLE

DATA/CLOCK

DDO0

DDO1/RCO

DATA

CLOCK

111

DATA

MUTE

CLOCK

MUTE

DATA

Power down

MUTE

Power down

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