After so much struggle i found solution for this problem. I am writing here because it may help some other person..

1. Repeating Sequence block is a masked subsystem block having the Lookup 1-d block underneath it in MATLAB R2013b and before. In current releases, the 1-d block is replaced by the new n-D Lookup table block. The n-D lookup table block only accepts strictly monotonic values.

2. A workaround to this issue can be to change it to [0 0.00002 0.00002+eps].

'eps' is the smallest floating-point number that can be recognized by MATLAB. Its value is 2^(-52).

If you change the value to [0 0.00002 0.00002+eps] in repeating sequence generator. can find that the error is not occurring

I also found the same issue .thanx a lot for the solution just relieved from the same issue. 

hello,Sreekanth Rtg!

           I meet the problem recently and I couldn't understand your solution. Could you please tell me which parameter in repeating sequence generator should be set as  [0 0.00002 0.00002+eps]. My MATLAB edition is R2015a, and I can only set two parameters in repeating sequence generator, they are Time values and Output values. I think neither of the two parameters should be set as  [0 0.00002 0.00002+eps]. Can you describe you solution detaily.

Thank you!

In a sawtooth waveform /|/|/| like this  falling from high value to low value takes place instantly. So if you set Time values like [0 0.00002 0.00002] and output values like [0  1 0]. matlab will give error. So change Time values to [0 0.00002 0.00002+eps] and keep output values same. Now error will not arise.

Thanks for your reply!  I understand now.@Sreekanth Rtg