File size: 5,532 Bytes
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module test;
`TBASSERT_METHOD(tbassert)
localparam BLOCKS = 3;
localparam WIDTH_IN = 2;
localparam WIDTH_SELECT = $clog2(WIDTH_IN); // do not pass this to the module because
// it is dependent value
// DUT inputs
reg Enable_bar;
reg [WIDTH_SELECT-1:0] Select; // Select is one bit
reg [BLOCKS*WIDTH_IN-1:0] A;
// DUT outputs
wire [BLOCKS-1:0] Y;
// DUT
ttl_74157 #(.BLOCKS(BLOCKS), .WIDTH_IN(WIDTH_IN), .DELAY_RISE(5), .DELAY_FALL(3)) dut(
.Enable_bar(Enable_bar),
.Select(Select),
.A_2D(A),
.Y(Y)
);
localparam SELECT_A = 1'b0;
localparam SELECT_B = 1'b1;
initial
begin
reg [WIDTH_IN-1:0] Block1;
reg [WIDTH_IN-1:0] Block2;
reg [WIDTH_IN-1:0] Block3;
$dumpfile("74157-tb.vcd");
$dumpvars;
// select A: enabled
Enable_bar = 1'b0;
Select = SELECT_A;
Block1 = 2'b11;
Block2 = 2'b11;
Block3 = 2'b10;
A = {Block3, Block2, Block1};
#6
tbassert(Y == 3'b011, "Test 1");
#0
// select A: disabled -> output 0s
Enable_bar = 1'b1;
#6
tbassert(Y == 3'b000, "Test 2");
#0
// select B: disabled
Select = SELECT_B;
#10
tbassert(Y == 3'b000, "Test 3");
#0
// select B: enabled
Enable_bar = 1'b0;
#10
tbassert(Y == 3'b111, "Test 4");
#0
// while enabled: change to select A from select B
Select = SELECT_A;
#10
tbassert(Y == 3'b011, "Test 5");
#0
// while select A enabled: change to different inputs
Block1 = 2'b10;
Block2 = 2'b01;
Block3 = 2'b01;
A = {Block3, Block2, Block1};
#10
tbassert(Y == 3'b110, "Test 6");
#0
// while enabled: change to select B from select A
Select = SELECT_B;
#10
tbassert(Y == 3'b001, "Test 7");
#0
// select B: disabled
Enable_bar = 1'b1;
#6
tbassert(Y == 3'b000, "Test 8");
#0
// select A: disabled
Select = SELECT_A;
#10
tbassert(Y == 3'b000, "Test 9");
#0
// select A: enabled and change to different inputs with null effect on output 0s
Enable_bar = 1'b0;
Block1 = 2'b10;
Block2 = 2'b00;
Block3 = 2'b00;
A = {Block3, Block2, Block1};
#10
tbassert(Y == 3'b000, "Test 10");
#0
// select B: enabled with null change to output 0s
Select = SELECT_B;
Block1 = 2'b00;
Block2 = 2'b01;
Block3 = 2'b00;
A = {Block3, Block2, Block1};
#10
tbassert(Y == 3'b000, "Test 11");
#0
// select B: all output bits transition from previous, direct from inputs
Block1 = 2'b10;
Block2 = 2'b11;
Block3 = 2'b10;
A = {Block3, Block2, Block1};
#6
tbassert(Y == 3'b111, "Test 12");
#0
// all output bits transition from previous, direct from select A
Block1 = 2'b01;
Block2 = 2'b10;
Block3 = 2'b10;
A = {Block3, Block2, Block1};
#6
tbassert(Y == 3'b110, "Test 13");
#0
Select = SELECT_A;
#6
tbassert(Y == 3'b001, "Test 13");
#0
// select A: all output bits transition from previous, on disable
Block1 = 2'b01;
Block2 = 2'b11;
Block3 = 2'b11;
A = {Block3, Block2, Block1};
#6
tbassert(Y == 3'b111, "Test 14");
#0
Enable_bar = 1'b1;
#10
tbassert(Y == 3'b000, "Test 14");
#0
// while enabled: change to select B from select A and change to different inputs
// with null effect on output 1s
Enable_bar = 1'b0;
#6
tbassert(Y == 3'b111, "Test 15");
#10
Select = SELECT_B;
Block1 = 2'b10;
Block2 = 2'b10;
Block3 = 2'b10;
A = {Block3, Block2, Block1};
#10
tbassert(Y == 3'b111, "Test 15");
#0
// timing: while enabled, clear/set inputs, then must wait for outputs to transition
Enable_bar = 1'b0;
Select = 1'bx;
Block1 = {WIDTH_IN{1'bx}};
Block2 = {WIDTH_IN{1'bx}};
Block3 = {WIDTH_IN{1'bx}};
A = {Block3, Block2, Block1};
#10
Select = SELECT_A;
Block1 = 2'b11;
Block2 = 2'b01;
Block3 = 2'b10;
A = {Block3, Block2, Block1};
#2
tbassert(Y === 3'bxxx, "Test 16");
#3
tbassert(Y == 3'b011, "Test 16");
#0
// timing: while enabled, clear/set inputs, then must wait for outputs to transition,
// off the select input only
Enable_bar = 1'b0;
Select = 1'bx;
Block1 = {WIDTH_IN{1'bx}};
Block2 = {WIDTH_IN{1'bx}};
Block3 = {WIDTH_IN{1'bx}};
A = {Block3, Block2, Block1};
#10
Block1 = 2'b11;
Block2 = 2'b01;
Block3 = 2'b10;
A = {Block3, Block2, Block1};
#6
Select = SELECT_A;
#2
tbassert(Y === 3'bxxx, "Test 17");
#3
tbassert(Y == 3'b011, "Test 17");
#0
// timing: same, other select
Enable_bar = 1'b0;
Select = 1'bx;
Block1 = {WIDTH_IN{1'bx}};
Block2 = {WIDTH_IN{1'bx}};
Block3 = {WIDTH_IN{1'bx}};
A = {Block3, Block2, Block1};
#10
Block1 = 2'b10;
Block2 = 2'b11;
Block3 = 2'b11;
A = {Block3, Block2, Block1};
#6
Select = SELECT_B;
#2
tbassert(Y === 3'bxxx, "Test 18");
#3
tbassert(Y == 3'b111, "Test 18");
#0
// timing: while enabled, clear/set inputs, then must wait for outputs to transition,
// off the data inputs only
Select = 1'bx;
Block1 = {WIDTH_IN{1'bx}};
Block2 = {WIDTH_IN{1'bx}};
Block3 = {WIDTH_IN{1'bx}};
A = {Block3, Block2, Block1};
#10
Select = SELECT_B;
#6
Block1 = 2'b11;
Block2 = 2'b01;
Block3 = 2'b10;
A = {Block3, Block2, Block1};
#2
tbassert(Y === 3'bxxx, "Test 19");
#3
tbassert(Y == 3'b101, "Test 19");
#0
// timing: same, other select (with only the selected data input being set)
Select = 1'bx;
Block1 = {WIDTH_IN{1'bx}};
Block2 = {WIDTH_IN{1'bx}};
Block3 = {WIDTH_IN{1'bx}};
A = {Block3, Block2, Block1};
#10
Select = SELECT_A;
#6
Block1[0] = 1'b1;
Block2[0] = 1'b1;
Block3[0] = 1'b0;
A = {Block3, Block2, Block1};
#2
tbassert(Y === 3'bxxx, "Test 20");
#3
tbassert(Y == 3'b011, "Test 20");
#10
$finish;
end
endmodule
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