File size: 5,421 Bytes
8dc19e4 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 | // Test: Dual 2-line to 4-line decoder/demultiplexer (inverted outputs)
module test;
`TBASSERT_METHOD(tbassert)
localparam BLOCKS = 3;
localparam WIDTH_OUT = 2;
localparam WIDTH_IN = $clog2(WIDTH_OUT); // do not pass this to the module because
// it is dependent value
// DUT inputs
reg [BLOCKS-1:0] Enable_bar;
reg [BLOCKS*WIDTH_IN-1:0] A; // WIDTH_IN is one bit
// DUT outputs
wire [BLOCKS*WIDTH_OUT-1:0] Y;
// DUT
ttl_74139 #(.BLOCKS(BLOCKS), .WIDTH_OUT(WIDTH_OUT), .DELAY_RISE(5), .DELAY_FALL(3)) dut(
.Enable_bar(Enable_bar),
.A_2D(A),
.Y_2D(Y)
);
initial
begin
reg [WIDTH_IN-1:0] AInputs;
reg [WIDTH_IN-1:0] BInputs;
reg [WIDTH_IN-1:0] CInputs;
reg [WIDTH_OUT-1:0] XOutputs;
reg [WIDTH_OUT-1:0] YOutputs;
reg [WIDTH_OUT-1:0] ZOutputs;
$dumpfile("74139-tb.vcd");
$dumpvars;
// select A: enabled -> first output is 0
Enable_bar = {BLOCKS{1'b0}};
AInputs = 1'b0;
BInputs = 1'b0;
CInputs = 1'b0;
A = {CInputs, BInputs, AInputs};
#6
{ZOutputs, YOutputs, XOutputs} = Y;
tbassert(XOutputs == 2'b10, "Test 1");
tbassert(YOutputs == 2'b10, "Test 1");
tbassert(ZOutputs == 2'b10, "Test 1");
#0
// select A: disabled in first block -> output is 11 instead of 10
Enable_bar[0] = 1'b1;
#6
{ZOutputs, YOutputs, XOutputs} = Y;
tbassert(XOutputs == 2'b11, "Test 2");
tbassert(YOutputs == 2'b10, "Test 2");
tbassert(ZOutputs == 2'b10, "Test 2");
#0
// select A: disabled in second block, enabled in first block
Enable_bar[0] = 1'b0;
Enable_bar[1] = 1'b1;
#6
{ZOutputs, YOutputs, XOutputs} = Y;
tbassert(XOutputs == 2'b10, "Test 3");
tbassert(YOutputs == 2'b11, "Test 3");
tbassert(ZOutputs == 2'b10, "Test 3");
#0
// select B: disabled -> output 1s
Enable_bar = {BLOCKS{1'b1}};
AInputs = 1'b1;
BInputs = 1'b1;
CInputs = 1'b1;
A = {CInputs, BInputs, AInputs};
#10
{ZOutputs, YOutputs, XOutputs} = Y;
tbassert(XOutputs == 2'b11, "Test 4");
tbassert(YOutputs == 2'b11, "Test 4");
tbassert(ZOutputs == 2'b11, "Test 4");
#0
// select B: enabled in second and third blocks -> second output is 0 where enabled
Enable_bar[1] = 1'b0;
Enable_bar[2] = 1'b0;
#10
{ZOutputs, YOutputs, XOutputs} = Y;
tbassert(XOutputs == 2'b11, "Test 5");
tbassert(YOutputs == 2'b01, "Test 5");
tbassert(ZOutputs == 2'b01, "Test 5");
#0
// select A: enabled in second and third blocks -> first output is 0 where enabled
A = {BLOCKS{1'b0}};
#10
{ZOutputs, YOutputs, XOutputs} = Y;
tbassert(XOutputs == 2'b11, "Test 6");
tbassert(YOutputs == 2'b10, "Test 6");
tbassert(ZOutputs == 2'b10, "Test 6");
#0
// select A: enabled in first and third blocks
Enable_bar[0] = 1'b0;
Enable_bar[1] = 1'b1;
Enable_bar[2] = 1'b0;
#10
{ZOutputs, YOutputs, XOutputs} = Y;
tbassert(XOutputs == 2'b10, "Test 7");
tbassert(YOutputs == 2'b11, "Test 7");
tbassert(ZOutputs == 2'b10, "Test 7");
#0
// while enabled: change to select B from select A -> second output is 0
Enable_bar[1] = 1'b0;
#10
{ZOutputs, YOutputs, XOutputs} = Y;
tbassert(XOutputs == 2'b10, "Test 8");
tbassert(YOutputs == 2'b10, "Test 8");
tbassert(ZOutputs == 2'b10, "Test 8");
#0
A = {BLOCKS{1'b1}};
#10
{ZOutputs, YOutputs, XOutputs} = Y;
tbassert(XOutputs == 2'b01, "Test 8");
tbassert(YOutputs == 2'b01, "Test 8");
tbassert(ZOutputs == 2'b01, "Test 8");
#0
// while disabled: change to select A from select B with null change to output 1s
Enable_bar = {BLOCKS{1'b1}};
#10
{ZOutputs, YOutputs, XOutputs} = Y;
tbassert(XOutputs == 2'b11, "Test 9");
tbassert(YOutputs == 2'b11, "Test 9");
tbassert(ZOutputs == 2'b11, "Test 9");
#0
A = {BLOCKS{1'b0}};
#10
{ZOutputs, YOutputs, XOutputs} = Y;
tbassert(XOutputs == 2'b11, "Test 9");
tbassert(YOutputs == 2'b11, "Test 9");
tbassert(ZOutputs == 2'b11, "Test 9");
#0
// while enabled: mixed selects -> outputs are both 01, 10
Enable_bar = {BLOCKS{1'b0}};
AInputs = 1'b1;
BInputs = 1'b0;
CInputs = 1'b0;
A = {CInputs, BInputs, AInputs};
#10
{ZOutputs, YOutputs, XOutputs} = Y;
tbassert(XOutputs == 2'b01, "Test 10");
tbassert(YOutputs == 2'b10, "Test 10");
tbassert(ZOutputs == 2'b10, "Test 10");
#0
// while enabled: change to select B from select A in third block only
CInputs = 1'b1;
A = {CInputs, BInputs, AInputs};
#6
{ZOutputs, YOutputs, XOutputs} = Y;
tbassert(XOutputs == 2'b01, "Test 11");
tbassert(YOutputs == 2'b10, "Test 11");
tbassert(ZOutputs == 2'b01, "Test 11");
#0
// same selects but disabled in first block -> output is 11 instead of 01
Enable_bar[0] = 1'b1;
#6
{ZOutputs, YOutputs, XOutputs} = Y;
tbassert(XOutputs == 2'b11, "Test 12");
tbassert(YOutputs == 2'b10, "Test 12");
tbassert(ZOutputs == 2'b01, "Test 12");
#0
// same selects but disabled in second block, enabled in first block -> output is 11
// instead of 10
Enable_bar[0] = 1'b0;
Enable_bar[1] = 1'b1;
#6
{ZOutputs, YOutputs, XOutputs} = Y;
tbassert(XOutputs == 2'b01, "Test 13");
tbassert(YOutputs == 2'b11, "Test 13");
tbassert(ZOutputs == 2'b01, "Test 13");
#0
// all input selects transition from previous
AInputs = 1'b0;
BInputs = 1'b1;
CInputs = 1'b0;
A = {CInputs, BInputs, AInputs};
#6
{ZOutputs, YOutputs, XOutputs} = Y;
tbassert(XOutputs == 2'b10, "Test 14");
tbassert(YOutputs == 2'b11, "Test 14");
tbassert(ZOutputs == 2'b10, "Test 14");
#10
$finish;
end
endmodule
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