The 16-bit Scrambler/De-scrambler allows scrambling and de-scrambling of two 8-bit PCI Express symbols in parallel. It is intended to be used with PHY chips using 16-bit PIPE interface (e.g., TI XIO1100 x1 PHY).
The purpose of the scrambler is to eliminate a repetitive pattern on the data stream. A repetitive pattern on a 2.5Gbs PCI Express data stream (such as 10101010) can generate significant EMI noise. By scrambling the data stream repetitive patterns are eliminated and thus spread the EMI energy over a broader range in the spectrum. This scrambling technique is often referred to as spread spectrum and is an effective way of whitening the noise.
Standard deliverables include an Actel-targeted netlist or fully-synthesizable VHDL/Verilog RTL, Simulation models and testbench, Comprehensive user's guide, Timing constraint files, and Technical support.
- Scrambling is applied to Data characters associated with DLLPs and TLPs including logical idles and TS1 and TS2 ordered sets
- K characters are not scrambled and bypass the scrambling logic
- Compliance-pattern-related characters are not scrambled
- When a COM character exits the scrambler the COM does not get scrambled, but it initializes the LFSR to 16ÔÇÖhFFFF
- COM character initializes the de-scrambler to 16ÔÇÖhFFFF
- LFSR does not advance on SKP characters
- Designed specifically for the Actel ProASIC3 and derivatives
- Uses 143 of 24,576 Tiles (less than 1%) of an Actel ProASIC3 A3P1000 Device