
PM5317 SPECTRA-9953 Telecom Standard Product Data Sheet
Release
Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.
Document No.: PMC-2000741, Issue 5
122
14.24 LVDS Receiver
The RXLV block is a 777.6 Mbit/s LVDS receiver according to the IEEE 1596.3-1996 LVDS
specification including the minor differences noted in the Line LVDS Overview at the
beginning of the Functional Description.
The RXLV block is the receiver shown in Figure 6. It accepts up to 777.6 Mbit/s LVDS signals
from the transmitter, over RP[X]/RN[X] pins, amplifying them and converting them to digital
signals, then passing them to a data recovery unit (DRU). Holding to the IEEE 1596.3-1996
specification, the RXLV has a differential input sensitivity better than 100 mV.
These are LVDS receivers not CMOS. If a link is unused there is no electrical problem in
leaving AD+/AD- floating (as opposed to a CMOS input). Power dissipation is the same
regardless of whether the input is connected or not. No damage to the device will occur.
If the user knows a link is not used, they should disable it in software. This way, the power for
that link will be nearly none. There is no requirement for how quickly this should be done. It
simply results in lower power dissipation since circuitry will be shut down. This is not
mandatory for the device to operate properly but is a good practice since it improves margins.
In terms of hot-swap, there is no problem. The channel can be left enabled at all time and the
device will sync up once the far end transmitter is connected. There will be no effect on other
channels.
A total of 16 RXLV blocks are instantiated in the SPECTRA-9953 device.
14.25 Add bus Data Recovery Unit
The DRU is a fully integrated data recovery and serial-to-parallel converter which can be used
for 777.6 Mbit/s NRZ data. 8B/10B block code is used to guarantee transition density for
optimal performance.
The DRU recovers data and outputs a 10-bit word synchronized with a line rate divided by 10-
gated clock to allow frequency deviations between the data source and the local oscillator. The
output clock is not a recovered clock. The DRU accumulates 10 data bits, without regard to
8B/10B character boundaries, and outputs them on the next clock edge. If 10 bits are not
available for transfer at a given clock cycle, the output clock is gated.
The DRU provides moderate high frequency jitter tolerance suitable for inter-chip serial link
applications. It can support frequency deviations up to 100ppm.
There are 16 instances of the DRU on the SPECTRA-9953 device.