DSP Signal Generator Implementation On C6713 DSK - ComLab

Symbol Block Level (in hex)
000 0x7FFF
001 0x5B6D
010 0x36DB
011 0x1249
100 -0x1249
101 -0x36DB
110 -0x5B6D
111 -0x7FFF
Figure 3.24: 4-level PAM lookup table for mapping
Figure 3.25 shows source code for generating 8-level PAM.
1 int i_8PAM_M, j_8PAM_M, masked_value, initial, output, assign, data_8PAM[8];
2 short k=0;
3 interrupt void c_int11() //interrupt service routine
4 {
5 if (i_8PAM_M==60) //new input is taken every 60 samples
6 {sample_data = input_sample(); //inputs data
7 sample_data = sample_data >> 1; //least significant bit discarded
8 i_8PAM_M=0;
9 j_8PAM_M=0;}
10 masked_value = sample_data & 0x0007; //masks sample as 3-bit segments
11 output = data_8PAM[masked_value]; //gets corresponding level
12 output_sample(output); //outputs corresponding voltage level 12 times
13 j_8PAM_M++; //repeated output counter
14 if (j_8PAM_M==12) //checks if repetition is over
15 {j_8PAM_M=0;
16 sample_data = sample_data >> 3;} //shifts input to mask next segment
17 i_8PAM_M++;
18 return;
19 } // end of interrpt routine
20 void main()
21 {initial=0x7FFF;
22 for(k=0; k