1、.1n 應(yīng)用 數(shù)字信號處理和數(shù)字通信n 地位 影響系統(tǒng)的運行速度n 實現(xiàn)l 并行乘法器l 移位相加乘法器l 查找表乘法器l 加法樹乘法器.29.2.1 并行乘法器l 結(jié)構(gòu) 用乘法運算符描述 由EDA軟件綜合l 優(yōu)點 運算速度快l 缺點 耗用資源多.3【例9.4】8位并行乘法器module mult( outcome, a, b);parameter size = 8;inputsize:1 a, b; / 源操作數(shù)output2*size:1 outcome; / 乘積assign outcome = a*b; / 相乘endmodule.48位并行乘法器RTL圖.59.2.2 移位相加乘法器

2、l 結(jié)構(gòu) 移位寄存器 加法器l 優(yōu)點 耗用資源少.6【例9.16】8位二進制數(shù)的乘法module mult_for( outcome, a, b );parameter size = 8;inputsize:1 a, b;output2*size:1 outcome;reg2*size:1 outcome;integer i;.7always ( a or b )begin outcome = 4h0;for( i = 1; i = size; i = i+1 ) if( bi ) outcome = outcome + ( a (i-1) );endendmodule.8乘法器的功能仿真波形

3、圖.99.2.3 查找表乘法器l 結(jié)構(gòu) 操作數(shù)：地址 乘積：存儲器l 優(yōu)點 運算速度快l 缺點 耗用存儲資源多.10l 設(shè)計思路n 4位查找表乘法器 Y = AB A = A122+A2 B = B122+B2 則 Y = ( A122+A2 )( B122+B2 ) = A1B124 + A1B222 + A2B122 + A2B2.11n 8位查找表乘法器 Y = AB A = A124+A2 B = B124+B2 則 Y = ( A124+A2 )( B124+B2 ) = A1B128 + A1B224 + A2B124 + A2B2.12【例9.5】 88查找表乘法器/* 22查找

4、表乘法器 */module lookup( out, a, b, clk );output3:0 out; / 乘積input1:0 a, b; / 操作數(shù)input clk;reg3:0 out;reg3:0 address; / 存儲器地址.13always ( posedge clk )beginaddress = a, b ;case( address )4h0:out = 4b0000;4h1:out = 4b0000;4h2:out = 4b0000;4h3:out = 4b0000;4h4:out = 4b0000;4h5:out = 4b0001;4h6:out = 4b001

5、0;4h7:out = 4b009;.144h8:out = 4b0000;4h9:out = 4b0010;4ha:out = 4b0100;4hb:out = 4b090;4hc:out = 4b0000;4hd:out = 4b009;4he:out = 4b090;4hf:out = 4b1001;default: out = 4bx;endcaseendendmodule.15/* 44查找表乘法器 */module mult4x4( out, a, b, clk );output7:0 out; / 乘積input3:0 a, b; / 操作數(shù)input clk;reg7:0 ou

6、t;reg1:0 firsta, firstb; / 操作數(shù)高2位reg1:0 seconda, secondb; / 操作數(shù)低2位wire3:0 outa, outb, outc, outd; / 乘積每2位1組.16always ( posedge clk )beginfirsta = a3:2;seconda = a1:0;firstb = b3:2;secondb = b1:0;end.17lookup m1( outa, firsta, firstb, clk ), / 元件調(diào)用 m2( outb, firsta, secondb, clk ), m3( outc, seconda,

7、 firstb, clk ), m4( outd, seconda, secondb, clk );always ( posedge clk )beginout = ( outa 4 ) + ( outb 2 ) / 乘積 + ( outc 2 ) + outd;endendmodule.184位查找表乘法器仿真波形圖.19/* 88查找表乘法器 */module mult8x8( out, a, b, clk );output15:0 out; / 乘積input7:0 a, b; / 操作數(shù)input clk;reg15:0 out;reg3:0 firsta, firstb; / 操作數(shù)

8、高4位reg3:0 seconda, secondb; / 操作數(shù)低4位wire7:0 outa, outb, outc, outd; / 乘積每8位1組.20always ( posedge clk )beginfirsta = a7:4;seconda = a3:0;firstb = b7:4;secondb = b3:0;end.21mult4x4 n1( outa, firsta, firstb, clk ), / 元件調(diào)用 n2( outb, firsta, secondb, clk ), n3( outc, seconda, firstb, clk ), n4( outd, sec

9、onda, secondb, clk );always ( posedge clk )beginout = ( outa 8 ) + ( outb 4 ) / 乘積 + ( outc 4 ) + outd;endendmodule.228位查找表乘法器仿真波形圖.239.2.4 加法樹乘法器l 結(jié)構(gòu) 底層：乘法器 高層：多級加法器l 優(yōu)點 1個時鐘周期完成.24加法樹乘法器結(jié)構(gòu)框圖81乘法器a128b781乘法器a64b6加法器81乘法器a32b581乘法器a16b4加法器81乘法器a8b381乘法器a4b2加法器81乘法器a2b181乘法器ab0加法器加法器加法器加法器y=ab.25【例9.

10、6】8位加法樹乘法器module add_tree( out, a, b, clk );output15:0 out; / 乘積input7:0 a, b; / 操作數(shù)input clk;wire15:0 out;wire15:0 out1, c1; / 加法器和wire13:0 out2;wire11:0 out3, c2;wire9:0 out4;.26reg14:0 temp0; / 最高位乘積reg13:0 temp1;reg12:0 temp2;reg11:0 temp3;reg10:0 temp4;reg9:0 temp5;reg8:0 temp6;reg7:0 temp7; /

11、最低位乘積.27/* 81乘法器 */function7:0 mult8x1;input7:0 operand;input sel;beginmult8x1 = ( sel ) ? ( operand ) : 8b00000000;endendfunction.28/* 操作數(shù)b各位與操作數(shù)a相乘 */always ( posedge clk )begintemp7 = mult8x1( a, b0 );temp6 = ( mult8x1( a, b1 ) ) 1;temp5 = ( mult8x1( a, b2 ) ) 2;temp4 = ( mult8x1( a, b3 ) ) 3;tem

12、p3 = ( mult8x1( a, b4 ) ) 4;temp2 = ( mult8x1( a, b5 ) ) 5;temp1 = ( mult8x1( a, b6 ) ) 6;temp0 = ( mult8x1( a, b7 ) ) 7;end.29/* 加法器樹運算 */assign out1 = temp0 + temp1;assign out2 = temp2 + temp3;assign out3 = temp4 + temp5;assign out4 = temp6 + temp7;assign c1 = out1 + out2;assign c2 = out3 + out4;a

13、ssign out = c1 + c2;endmodule.308位加法樹乘法器仿真波形圖.31四種乘法器的比較.32.33【例9.30】乘累加器（MAC）module MAC( out, opa, opb, clk, clr );output15:0 out;input7:0 opa, opb;input clk, clr;wire15:0 sum;reg15:0 out;.34function15:0 mult;input7:0 opa, opb;reg 15:0 result;integer i;begin result = opa0 ? opb : 0; for(i = 1; i = 7; i = i+1)begin