GS2986 Datasheet, PDF (23/41 Pages) Gennum Corporation – Standards indication in Auto mode

will only lock to the data rate selected in accordance with Table 4-7.
Table 4-7: Data Rate Indication/Selection Bit Pattern
SS[1:0]
0
1
2
3
Data Rate (Mb/s)
Reserved
270
1485 or 1485/1.001
2970 or 2970/1.001
4.11 SD/HD Indication
The SD/HD signal indicates the output data rate of the device and can be connected to the
SD/HD input pin of dual slew rate cable drivers such as the GS2988.
When this signal is HIGH, the data rate is 270Mb/s. This signal is LOW for all other data rates.
This signal is also LOW when the device is operating in bypass mode (Auto-bypass and
User-bypass).
The SD/HD signal is LOW when the device is not locked.
4.12 Bypass Mode
In bypass mode, the GS2986 passes the data at the inputs, directly to the output. There are two
register bits that control the bypass function: BYPASS and AUTOBYPASS.
The BYPASS bit is an active-high signal which forces the GS2986 into bypass mode for as long
as the bit is asserted HIGH.
The AUTOBYPASS bit is an active-high signal that places the GS2986 into bypass mode only
when the PLL has not locked to a data rate.
Table 4-8: Bypass Modes
Bypass
HIGH
LOW
LOW
Autobypass
X
HIGH
LOW
Device Operation
Bypass Mode
Bypass Mode if the PLL has not
locked to a data rate
Power-up default. Normal
Operation, part always tries to
lock to the incoming data
stream.
Note that if BYPASS is HIGH, this will override the AUTOBYPASS functionality.
When the GS2986's PLL is not locked and BYPASS = LOW and AUTOBYPASS = LOW, the serial
digital output DDO/DDO will produce invalid data.
GS2986 Multi-Rate SDI Reclocker with Equalization &
De-emphasis
Data Sheet
52134 - 3
July 2012
23 of 41