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cse141L-project/RTL/program3_tb.sv
2022-08-19 20:24:19 -07:00

156 lines
6.9 KiB
Systemverilog

// program3_tb
// testbench for programmable message decryption, space removal (Program #3)
// CSE141L
// runs program 2 (decrypt a message), but with corruption
module program3_tb ();
logic clk = 1'b0; // advances simulation step-by-step
logic init = 1'b1; // init (reset) command to DUT
logic start = 1'b1; // req (start program) command to DUT
wire done; // done flag returned by DUT
logic[3:0] pre_length; // space char. bytes before first char. in message
logic[7:0] message1[49]; // original raw message, in binary
logic[7:0] msg_padded1[80]; // original message, plus pre- and post-padding w/ ASCII spaces
logic[7:0] msg_crypto1[64]; // encrypted message according to the DUT
logic[6:0] lfsr_ptrn; // chosen one of 9 maximal length 7-tap shift reg. ptrns
logic[6:0] LFSR_ptrn[9]; // the 9 candidate maximal-length 7-bit LFSR tap ptrns
logic[6:0] lfsr1[64]; // states of program 1 encrypting LFSR
logic[6:0] LFSR_init; // one of 127 possible NONZERO starting states
int score; // count of correct encyrpted characters
// our original American Standard Code for Information Interchange message follows
// note in practice your design should be able to handle ANY ASCII string that is
// restricted to characters between space (0x20) and script f (0x9f) and shorter than
// 53 characters in length
string str1 = " four score and seven years ago...";
// displayed encrypted string will go here:
string str_enc1[64]; // program 1 desired output will go here
int strlen; // incoming string length
int pt_no; // select LFSR pattern, value 0 through 8
int file_no; // write to file
int space; // counts leading space characters in message
logic [5:0] flipper; // corruptor -- bit flip
logic [79:0] flipped = 80'b0; // tracks which word got a bit flipped
// the 9 possible maximal-length feedback tap patterns from which to choose
assign LFSR_ptrn[0] = 7'h60; // 110_0000
assign LFSR_ptrn[1] = 7'h48;
assign LFSR_ptrn[2] = 7'h78;
assign LFSR_ptrn[3] = 7'h72;
assign LFSR_ptrn[4] = 7'h6A;
assign LFSR_ptrn[5] = 7'h69;
assign LFSR_ptrn[6] = 7'h5C;
assign LFSR_ptrn[7] = 7'h7E;
assign LFSR_ptrn[8] = 7'h7B;
always_comb begin
pt_no = $urandom_range(0, 8);
if(pt_no>8) pt_no[3] = 0; // restrict pt_no to 0 through 8
lfsr_ptrn = LFSR_ptrn[pt_no]; // look up and engage the selected pattern; to data_mem[62]
end
// now select a starting LFSR state -- any nonzero value will do
always_comb begin
LFSR_init = $urandom;
if(!LFSR_init) LFSR_init = 7'b1; // prevents illegal starting state = 7'b0;
end
// set preamble length for the program run (always > 9 but < 26)
always_comb begin
pre_length = $urandom;
if(pre_length < 10) pre_length = 10; // prevents pre_length < 10
else if(pre_length > 26) pre_length = 26; // prevets pre_length > 26
end
// ***** instantiate your own top level design here *****
top_level dut(
.clk(clk), // input: use your own port names, if different
.init(init), // input: some prefer to call this ".reset"
.req(start), // input: launch program
.ack(done) // output: "program run complete"
);
initial begin
file_no = 'b1; // create your output file
#0ns strlen = str1.len; // length of string 1 (# characters between " ")
if(strlen>52) strlen = 52; // clip message at 52 characters
for(space=0;space<24;space++) // count leading spaces in message
if(str1[space]==8'h20) continue;
else break;
// program 1 -- precompute encrypted message
lfsr1[0] = LFSR_init; // any nonzero value (zero may be helpful for debug)
$fdisplay(file_no,"run encryption program; original message = ");
$fdisplay(file_no,"%s",str1); // print original message in transcript window
$fdisplay(file_no,"LFSR_ptrn = 0x%h, LFSR_init = 0x%h, pre_length: %d",lfsr_ptrn,LFSR_init,pre_length);
for(int j=0; j<80; j++) // pre-fill message_padded with ASCII space characters
msg_padded1[j] = 8'h20; //
for(int l=0; l<strlen; l++) // overwrite up to 49 of these spaces w/ message itself
msg_padded1[l+pre_length] = str1[l];
// compute the LFSR sequence
for (int ii=0;ii<63;ii++)
lfsr1[ii+1] = {(lfsr1[ii][5:0]),(^(lfsr1[ii]&lfsr_ptrn))};
// encrypt the message charater-by-character, then prepend the parity
// testbench will change on falling clocks to avoid race conditions at rising clocks
for (int i=0; i<64; i++) begin
msg_crypto1[i] = (msg_padded1[i] ^ lfsr1[i]);
msg_crypto1[i][7] = ^msg_crypto1[i][6:0]; // prepend parity bit into MSB
$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]);
str_enc1[i] = string'(msg_crypto1[i][6:0]);
end
$fdisplay(file_no,"encrypted string = ");
for(int jj=0; jj<64; jj++)
$fwrite(file_no,"%s",str_enc1[jj]);
$fdisplay(file_no,"\n");
// run encryption program first to know what to decrypt
// ***** load operands into your data memory *****
// ***** use your instance name for data memory and its internal core *****
for(int m=0; m<24; m++) // load first 24 characters of encrypted message into data memory
dut.DM.core[m+64] = msg_crypto1[m];
for(int n=24; n<64; n++) begin // load subsequent, possibly corrupt, encrypted message into data memory
// set flipper = 8 or higher to disable bit corruption
flipper = $random;//$random; // value between 0 and 63, inclusive
dut.DM.core[n+64] = msg_crypto1[n]^(1<<flipper);
if(flipper<8) flipped[n]=1;
end
#20ns init = 1'b0; // suggestion: reset = 1 forces your program counter to 0
#10ns start = 1'b0; // request/start = 1 holds your program counter
#60ns; // wait for 6 clock cycles of nominal 10ns each
wait(done); // wait for DUT's ack/done flag to go high
#10ns $fdisplay(file_no,"");
$fdisplay(file_no,"program 3:");
// ***** reads your results and compares to test bench
// ***** use your instance name for data memory and its internal core *****
for(int n=0; n<64; n++) begin
if(flipped[n+pre_length+space]) begin
if(dut.DM.core[n][7]) begin
$fdisplay(file_no, "error successfully flagged");
score++;
end
else begin
$fdisplay(file_no, "failed to flag error");
end
end
else if({flipped[n+pre_length+space],msg_padded1[n+pre_length+space][6:0]} == dut.DM.core[n]) begin
$fdisplay(file_no,"%d bench msg: %s %h dut msg: %h", n, msg_padded1[n+pre_length+space][6:0], msg_padded1[n+pre_length+space], dut.DM.core[n]);
score++;
end
else
$fdisplay(file_no,"%d bench msg: %s %h dut msg: %h OOPS!", n, msg_padded1[n+pre_length+space][6:0], msg_padded1[n+pre_length+space], dut.DM.core[n]);
end
$fdisplay(file_no,"score = %d/64",score);
#20ns $fclose(file_no);
#20ns $stop;
end
always begin // continuous loop
#5ns clk = 1; // clock tick
#5ns clk = 0; // clock tock
end
endmodule