GS2975A Datasheet, PDF (20/27 Pages) Gennum Corporation – HD-LINX® III Multi-Rate SDI Automatic Reclocker with Dual Differential Outputs

In Manual mode, the data rate can be programmed and the SS[2:0] pins become inputs.
In this mode, the search algorithm is disabled and the PLL will only lock to the data rate
selected.
Table 4-2 shows the SS[2:0] pin settings for either the data rate selected (in Manual
mode) or the data rate that the PLL has locked to (in Auto mode).
Table 4-2: Data Rate Indication/Selection Bit Pattern
SS[2:0]
010
101
110
Data Rate (Mb/s)
270
1485 (1483.5)
2970 (2967)
4.8 Bypass Mode
In Bypass mode, the GS2975A passes the data at the inputs directly to the outputs. There
are two pins that control the bypass function: BYPASS and AUTOBYPASS.
When BYPASS is set HIGH, the GS2975A will be in Bypass mode.
When AUTOBYPASS is set HIGH, the GS2975A will be configured to enter Bypass mode
only when the PLL has not locked to a data rate. When BYPASS is set HIGH,
AUTOBYPASS will be ignored.
When the PLL is not locked, and both BYPASS and AUTOBYPASS are set LOW, the serial
digital output DDO0/DDO0 or DDO1/DDO1 will produce invalid data.
4.9 DVB-ASI Operation
The GS2975A will also re-clock DVB-ASI at 270 Mb/s. In auto mode, the device will
automatically lock to the incoming 270Mb/s signal. In manual mode, the SS[2:0] pins
must be set to 010 (270 Mb/s) to ensure proper operation.
4.10 Lock and LOS
The LOCKED signal is an active high output which indicates when the PLL is locked.
The internal lock logic of the GS2975A includes a system which monitors the Frequency
Acquisition Loop and the Phase Acquisition Loop as well as a monitor to detect harmonic
lock.
The LOS (Loss of Signal) output is an active HIGH output which indicates the absence of
data transitions at the DDIx input. In order for this output to be asserted, transitions must
not be present for a period of t_LA = 5 - 10μs. After this output has been asserted, LOS will
de-assert within t_LD = 0 - 5μs after the appearance of a transition at the DDIx input.
GS2975A HD-LINX® III Multi-Rate SDI Automatic
Reclocker with Dual Differential Outputs
Data Sheet
41487 - 4
April 2009
20 of 27