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sc_wrap in SystemC

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sc_fixed<5,5> sx;
sc_fixed<4,4,SC_TRN,SC_WRAP> sy0;
sc_fixed<4,4,SC_TRN,SC_WRAP,1> sy1;
sc_fixed<4,4,SC_TRN,SC_WRAP,2> sy2;
sc_fixed<4,4,SC_TRN,SC_WRAP,3> sy3;


The simulation results are as below.


sx = 9;    //sx   = 0b01001
sy0 = sx; //sy0 = 0b1001
sy1 = sx; //sy1 = 0b0001
sy2 = sx; //sy2 = 0b0101
sy3 = sx; //sy3 = 0b0111


sx = -5;   //sx   = 0b11011
sy0 = sx; //sy0 = 0b1011
sy1 = sx; //sy1 = 0b1011
sy2 = sx; //sy2 = 0b1011

sy3 = sx; //sy3 = 0b1011 //The definition in IEEE Std 1666™-2011 is "SC_WRAP, (n_bits>1)                         The result number shall get the sign bit of the original number. The saturated bits shall get the inverse value of the sign bit of the original number. The remaining bits shall be copied from the original number". So it seems the result should be sy3=0b1001.Can anybody tell me why the result is 0b1011? Thanks in advance. 

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