Answers to Questions in Xilinx Reed-Solomon Tutorial 1

Q1. Code rate = k/n = 187/207 = 0.903

Q2. Reed-Solomon codes can correct (n - k)/2 errors => (207 - 187)/2 => 10

Q3.  p(x) = x8 + x7 + x2 + x + 1 => 110000111 => 391

Q4. The series of exponents is: 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20 The increment index of this series is 1, so h=1. Dividing the first element by h gives Generator Start=1.

Here is the completed parameter table: Parameter Value Symbol Width 8 k 187 n 207 Field Polynomial (decimal) 391 Generator Start 1 h 1

Q5. The code is obfuscated (unreadable).

Q6. Latency=3 clock cycles. If you had selected area optimization in the configuration GUI, the latency would be 2 clock cycles.

Q7. The first check symbol should appear at 3940 ns. This is because start is sampled at 140 ns, then it takes 187*20 ns to process the information symbols, then the 3*20 ns latency must be accounted for i.e. 140+3740+60=3940 ns.

Q8. Depends on the specification of your machine. For a PIII 450MHz with 128MByte of RAM it takes about 3 minutes to complete the simulation.

Q9. Alot less time than it took when using the back-annotated netlist model!