GS2985 datasheet(26/45 Pages) SEMTECH

26 / 45 page

GS2985 Multi-Rate SDI Reclocker with Equalization &

De-emphasis

Data Sheet

36663 - 5

July 2012

26 of 45

Proprietary & Confidential

4.12 Bypass Mode

In bypass mode, the GS2985 passes the data at the inputs, directly to the output. There

are two pins that control the bypass function: BYPASS and AUTOBYPASS.

The BYPASS pin is an active-high signal which forces the GS2985 into bypass mode for

as long as the pin is asserted HIGH.

The AUTOBYPASS pin is an active-high signal that places the GS2985 into bypass mode

only when the PLL has not locked to a data rate.

Note that if BYPASS is HIGH, this will override the AUTOBYPASS functionality.

When the GS2985's PLL is not locked and BYPASS = LOW and AUTOBYPASS = LOW, the

serial digital output DDO/DDO will produce invalid data.

The AUTOBYPASS function will bypass unsupported (non-reclocked) SMPTE SDI signal

rates without producing bit errors: 143Mb/s, 177Mb/s, 360Mb/s, 540Mb/s.

4.13 DVB-ASI

The GS2985 also reclocks DVB-ASI signals at 270Mb/s. In auto mode, the device will

automatically lock to the incoming 270Mb/s signal. In manual mode, the SS[1:0] bits

must be set to 01 (270Mb/s) to ensure proper operation.

4.14 Output Mute and Data/Clock Output Selection

The DATA_MUTE pin is provided to allow muting of the serial digital data output.

Setting DATA_MUTE = LOW will force the serial digital outputs DDO/DDO to mute

(statically latch HIGH) under all conditions and operating modes.

The DDO1_DISABLE pin is provided to allow the second data/clock output to be

powered down.

When DDO1_DISABLE is set LOW, the serial digital clock outputs DDO1/RCO and

DDO1/RCO are muted and the driver is powered-down.

The DATA/CLOCK pin is provided to allow the second output to emit a copy of the

reclocked serial data or the recovered clock.

Table 4-9: Bypass Modes

Bypass

Autobypass

Device Operation

HIGH

Bypass Mode

LOW

HIGH

Bypass Mode if the PLL has not

locked to a data rate

LOW

Power-up default. Normal

Operation, part always tries to

lock to the incoming data

stream.

GS2985 Datasheet(PDF) 26 Page - Semtech Corporation

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