149 lines
6.8 KiB
Systemverilog
149 lines
6.8 KiB
Systemverilog
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// program1_tb
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// testbench for programmable message encryption (Program #1)
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// CSE141L
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// runs program 1 (encrypt a message)
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module program1_tb ();
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// DUT interface -- four one-bit wires, three to DUT, one from
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bit clk; // advances simulation step-by-step
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bit init = 1'b1; // init (reset) command to DUT
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bit start = 1'b1; // request (start program) command to DUT
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wire done; // acknowledge (program done) flag returned by DUT
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// test bench parameters
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logic [7:0] pre_length; // number of space char. before message itself, sent to data_mem[61]
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logic [7:0] message1[54]; // original raw message, in binary, up to 54 characters in length
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logic [7:0] msg_padded1[64]; // original message, plus pre- and post-padding w/ ASCII spaces
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logic [7:0] msg_crypto1[64]; // encrypted message returned by DUT
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logic [7:0] lfsr_ptrn; // choses one of 9 maximal length 7-tap shift reg. patterns
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logic [7:0] LFSR_ptrn[9]; // the 9 candidate maximal-length 7-bit LFSR tap ptrns themselves
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logic [7:0] lfsr1[64]; // states of program 1 encrypting LFSR
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logic [7:0] LFSR_init; // one of 127 possible NONZERO starting states for encrypting LFSR
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int score; // count of correctly encyrpted characters
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// our original American Standard Code for Information Interchange message follows
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// note in practice your design should be able to handle ANY ASCII string that is
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// restricted to characters between space (0x20) and script f (0x9f) and shorter than
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// 55 characters in length
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string str1 = "Mr. Watson, come here. I want to see you.";
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// displayed encrypted string will go here:
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string str_enc1[64]; // program 1 desired output will go here
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int strlen; // length of incoming message string itself, before padding
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logic [3:0] pt_no; // select LFSR pattern, index value 0 through 8
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int file_no; // output file tag (set to 1 for write to console/transcript)
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// the 9 possible 7-tap maximal-length feedback tap patterns from which to choose
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assign LFSR_ptrn[0] = 8'h60;
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assign LFSR_ptrn[1] = 8'h48;
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assign LFSR_ptrn[2] = 8'h78;
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assign LFSR_ptrn[3] = 8'h72;
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assign LFSR_ptrn[4] = 8'h6A;
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assign LFSR_ptrn[5] = 8'h69;
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assign LFSR_ptrn[6] = 8'h5C;
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assign LFSR_ptrn[7] = 8'h7E;
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assign LFSR_ptrn[8] = 8'h7B;
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always_comb begin
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pt_no = $random;
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if(pt_no>8) pt_no[3] = 0; // restrict pt_no to 0 through 8
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lfsr_ptrn = LFSR_ptrn[pt_no]; // look up and engage the selected pattern; to data_mem[62]
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end
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// now select a starting LFSR state -- any nonzero value will do
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always_comb begin
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LFSR_init = $random;
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if(!LFSR_init) LFSR_init = 7'b1; // prevents illegal starting state = 7'b0;
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end
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// set preamble length for the program run (always > 9 but < 26)
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always_comb begin
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pre_length = $random;
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if(pre_length < 10) pre_length = 10; // prevents pre_length < 10
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else if(pre_length > 26) pre_length = 26; // prevets pre_length > 26
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end
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// ***** instantiate your own top level design here *****
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top_level dut(
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.clk(clk), // input: use your own port names, if different
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.init(init), // input: some prefer to call this ".reset"
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.req(start), // input: launch program
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.ack(done) // output: "program run complete"
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);
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initial begin
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file_no = 'b1;
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//file_no = $fopen("msg_enocder_out.txt","w");
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#0ns strlen = str1.len; // length of string 1 (# characters between " ")
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if(strlen>54) strlen = 54; // clip message at 54 characters
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// program 1 -- precompute encrypted message
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lfsr1[0] = LFSR_init; // any nonzero value (zero may be helpful for debug)
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$fdisplay(file_no,"run encryption program; original message = ");
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$fdisplay(file_no,"%s",str1); // print original message in transcript window
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$fdisplay(file_no,"pt_no = %d",pt_no);
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$fdisplay(file_no,"LFSR_ptrn = 0x%h, LFSR_init = 0x%h",lfsr_ptrn,LFSR_init);
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// will subtract 0x20 from each preamble and each message character
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for(int j=0; j<64; j++) // pre-fill message_padded with ASCII space characters
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msg_padded1[j] = 8'h20; //
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for(int l=0; l<strlen; l++) // overwrite up to 54 of these spaces w/ message itself
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msg_padded1[pre_length+l] = str1[l]; // test bench does the -0x20 offset now
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// compute and store the LFSR sequence
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for (int ii=0;ii<63;ii++)
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lfsr1[ii+1] = {(lfsr1[ii][5:0]),(^(lfsr1[ii]&lfsr_ptrn))};
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// encrypt the message character-by-character, then prepend the parity
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// testbench will change on falling clocks to avoid race conditions at rising clocks
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for (int i=0; i<64; i++) begin
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msg_crypto1[i] = ((msg_padded1[i]-32) ^ lfsr1[i]);
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msg_crypto1[i][7] = 'b0;//^msg_crypto1[i][6:0]; // prepend parity bit into MSB
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$fdisplay(file_no,"i=%d, msg_pad=0x%h, lfsr=%b msg_crypt w/ parity = 0x%h", i,msg_padded1[i],lfsr1[i],msg_crypto1[i]);
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// for display purposes only, add 8'h20 to avoid nonprintable characters (<8'h20)
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str_enc1[i] = string'(msg_crypto1[i][6:0]+'h20);
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end
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$fdisplay(file_no,"encrypted string = ");
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for(int jj=0; jj<64; jj++)
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$fwrite(file_no,"%s",str_enc1[jj]);
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$fdisplay(file_no,"\n");
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// run encryption program
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// ***** load operands into your data memory *****
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// ***** use your instance name for data memory and its internal core *****
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for(int m=0; m<61; m++)
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dut.DM.core[m] = 8'h0; // pad memory w/ ASCII space characters
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for(int m=0; m<strlen; m++)
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dut.DM.core[m] = (str1[m]-8'h20); // overwrite/copy original string into device's data memory[0:strlen-1]
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dut.DM.core[61] = pre_length; // number of bytes preceding message
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dut.DM.core[62] = lfsr_ptrn; // LFSR feedback tap positions (9 permissible patterns)
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dut.DM.core[63] = LFSR_init; // LFSR starting state (nonzero)
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#20ns init = 1'b0; // suggestion: reset = 1 forces your program counter to 0
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#10ns start = 1'b0; // request/start = 1 holds your program counter
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#60ns; // wait for 6 clock cycles of nominal 10ns each
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wait(done); // wait for DUT's ack/done flag to go high
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#10ns $fdisplay(file_no,"");
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$fdisplay(file_no,"program 1:");
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// ***** reads your results and compares to test bench
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// ***** use your instance name for data memory and its internal core *****
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// the +'h20 restores the -32 bias, for better display visuals
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for(int n=0; n<64; n++) begin
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if(msg_crypto1[n]==dut.DM.core[n+64]) begin
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$fdisplay(file_no,"%d bench msg: %s %h dut msg: %h", n, msg_crypto1[n][6:0]+8'h20, msg_crypto1[n], dut.DM.core[n+64]);
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score++;
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end
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else
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$fdisplay(file_no,"%d bench msg: %s %h dut msg: %h OOPS!", n, msg_crypto1[n][6:0]+8'h20, msg_crypto1[n], dut.DM.core[n+64]);
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end
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$fdisplay(file_no,"score = %d/64",score);
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#20ns $fclose(file_no);
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#20ns $stop;
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end
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always begin // continuous loop
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#5ns clk = 1; // clock tick
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#5ns clk = 0; // clock tock
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end
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endmodule
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