Altera LVDS SERDES Transmitter / Receiver - Manual (Page 55)

Where:
• RSKM—is the timing margin between the receiver's clock input and the data input SW.
• Time unit interval (TUI)—is the time period of the serial data (1/f
MAX
). Also known as the LVDS
period in the TimeQuest Timing Analyzer section in the Quartus II Compilation Report.
• SW—is the period of time that the input data must be stable to ensure that data is successfully sampled
by the LVDS receiver. The SW is a device property and varies with device speed grade.
• RCCS— is the timing difference between the fastest and slowest input transitions, including t
CO
variations and clock skew. Specify RCCS by applying minimum and maximum
set_input_delay
constraints to the receiver inputs, where RCCS is the difference between the maximum and minimum
value.
To obtain accurate RSKM results in the TimeQuest analyzer, specify your RCCS figure using
set_input_delay
constraints.
The difference between your
set_input_delay -min
and
set_input_delay -max
must match your
RCCS figure.
For example, to specify an RCCS figure of 0.3 ns:
set_input_delay -clock rx_inclock -min 0 [get_ports {rx_in*}]
set_input_delay -clock rx_inclock -max 0.3 [get_ports {rx_in*}]
The TimeQuest analyzer takes the 0.3 ns RCCS figure into account during RSKM analysis.
The following figure shows the relationship between the RSKM, RCCS, and SW.
UG-MF9504
2014.12.15
Receiver Skew Margin and Transmitter Channel-to-Channel Skew 55
LVDS SERDES Transmitter/Receiver IP Cores User Guide Altera Corporation
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