170 lines
8.5 KiB
Systemverilog
170 lines
8.5 KiB
Systemverilog
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// program3_tb
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// testbench for programmable message decryption, space removal (Program #3)
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// CSE141L
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// runs program 2 (decrypt a message), but with corruption
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module program3_tb () ;
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logic clk = 1'b0 , // advances simulation step-by-step
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init = 1'b1 , // init (reset) command to DUT
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start = 1'b1 ; // req (start program) command to DUT
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wire done ; // done flag returned by DUT
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logic[3:0] pre_length ; // space char. bytes before first char. in message
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logic[7:0] message1[49] , // original raw message, in binary
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msg_padded1[80], // original message, plus pre- and post-padding w/ ASCII spaces
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msg_crypto1[64]; // encrypted message according to the DUT
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logic[6:0] lfsr_ptrn , // chosen one of 9 maximal length 7-tap shift reg. ptrns
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LFSR_ptrn[9] , // the 9 candidate maximal-length 7-bit LFSR tap ptrns
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lfsr1[64] , // states of program 1 encrypting LFSR
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LFSR_init ; // one of 127 possible NONZERO starting states
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int score ; // count of correct 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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// 53 characters in length
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string str1 = " four score and seven years ago..."; // sample program 1 input
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// string str1 = " Knowledge comes, but wisdom lingers. "; // alternative inputs
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// string str1 = " 01234546789abcdefghijklmnopqrstuvwxyz. "; // (make up your own,
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// string str1 = " f A joke is a very serious thing."; // as well)
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// string str1 = " Ajok "; //
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// string str1 = " Knowledge comes, but wisdom lingers. "; //
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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; // incoming string length
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int pt_no; // select LFSR pattern, value 0 through 8
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int file_no; // write to file
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int space; // counts leading space characters in message
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logic[5:0] flipper; // corruptor -- bit flip
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logic[79:0] flipped = 80'b0; // tracks which word got a bit flipped
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// the 8 possible maximal-length feedback tap patterns from which to choose
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assign LFSR_ptrn[0] = 7'h60; // 110_0000
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assign LFSR_ptrn[1] = 7'h48;
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assign LFSR_ptrn[2] = 7'h78;
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assign LFSR_ptrn[3] = 7'h72;
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assign LFSR_ptrn[4] = 7'h6A;
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assign LFSR_ptrn[5] = 7'h69;
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assign LFSR_ptrn[6] = 7'h5C;
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assign LFSR_ptrn[7] = 7'h7E;
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assign LFSR_ptrn[8] = 7'h7B;
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always_comb begin
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pt_no = $urandom_range(0, 8);
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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 = $urandom;
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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 = $urandom;
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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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//***** pre-load your instruction ROM here or inside itself *****
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// $readmemb("encoder.bin", dut.instr_rom.rom);
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// you may also pre-load desired constants, etc. into
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// your data_mem here -- the upper addresses are reserved for your use
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// dut.data_mem.DM[128]=8'hfe; //whatever constants you want
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file_no = 'b1; // create your output file
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#0ns strlen = str1.len; // length of string 1 (# characters between " ")
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if(strlen>52) strlen = 52; // clip message at 52 characters
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for(space=0;space<24;space++) // count leading spaces in message
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if(str1[space]==8'h20) continue;
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else break;
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// program 1 -- precompute encrypted message
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lfsr1[0] = LFSR_init; // any nonzero value (zero may be helpful for debug)
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$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,"LFSR_ptrn = 0x%h, LFSR_init = 0x%h, pre_length: %d",lfsr_ptrn,LFSR_init,pre_length);
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for(int j=0; j<80; 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 49 of these spaces w/ message itself
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msg_padded1[l+pre_length] = str1[l];
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// compute 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 charater-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] ^ lfsr1[i]);
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msg_crypto1[i][7] = ^msg_crypto1[i][6:0]; // prepend parity bit into MSB
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$fdisplay(file_no,"i=%d, msg_pad=0x%h, lfsr=%b msg_crypt w/ parity = 0x%h",
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i,msg_padded1[i],lfsr1[i],msg_crypto1[i]);
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str_enc1[i] = string'(msg_crypto1[i][6:0]);
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end
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$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 first to know what to decrypt
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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'h20; // 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]; // 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 possible ptrns)
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// dut.DM.core[63] = LFSR_init; // LFSR starting state (nonzero)
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for(int m=0; m<24; m++) // load first 24 characters of encrypted message into data memory
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dut.DM.core[m+64] = msg_crypto1[m];
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for(int n=24; n<64; n++) begin // load subsequent, possibly corrupt, encrypted message into data memory
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// set flipper = 8 or higher to disable bit corruption
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flipper = 8;//$random; // value between 0 and 63, inclusive
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dut.DM.core[n+64] = msg_crypto1[n]^(1<<flipper);
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if(flipper<8) flipped[n]=1;
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end
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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 3:");
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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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for(int n=0; n<64; n++) begin
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if(flipped[n+pre_length+space]) begin
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if(dut.DM.core[n][7]) begin
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$fdisplay(file_no, "error successfully flagged");
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score++;
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end else begin
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$fdisplay(file_no, "failed to flag error");
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end
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end
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else if({flipped[n+pre_length+space],msg_padded1[n+pre_length+space][6:0]}
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== dut.DM.core[n]) begin
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$fdisplay(file_no,"%d bench msg: %s %h dut msg: %h",
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n, msg_padded1[n+pre_length+space][6:0], msg_padded1[n+pre_length+space], dut.DM.core[n]);
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score++;
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end
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else
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$fdisplay(file_no,"%d bench msg: %s %h dut msg: %h OOPS!",
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n, msg_padded1[n+pre_length+space][6:0], msg_padded1[n+pre_length+space], dut.DM.core[n]);
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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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