条件语句、循环语句、块语句和生成语句.ppt

1、第5章 条件语句、循环语句、块语句和生成语句,5.1 条件语句（if else 语句）,5.1 条件语句（if else 语句）,5.1 条件语句（if else 语句）,5.1 条件语句（if else 语句）,5.1 条件语句（if else 语句）,5.1 条件语句（if else 语句）,5.2 case语句,5.2 case语句,5.2 case语句,5.2 case语句,5.2 case语句举例,reg 3:0 rega; reg 7:0 result; case(rega) 4 d0: result = 7 b10111111; 4 d1: result = 7 b1000011

2、0; 4 d2: result = 7 b11011011; 4 d3: result = 7 b11001111; 4 d4: result = 7 b11000110; 4 d5: result = 7 b11101101; 4 d6: result = 17 b1111101; 4 d7: result = 7 b10000111; 4 d8: result = 7 b11101111; 4 d9: result = 7 b11111111; default: result =7 bx; endcase,a,g,d,b,c,f,e,bit7,bit6,bit5,bit4,bit3,bit

3、2,bit1,bit0,g f e d c b a,LED驱动原理,5.2 case语句举例,reg 3:0 rega; reg 7:0 result; case(rega) 4 d0: result = 7 b10111111; 4 d1: result = 7 b10000110; 4 d2: result = 7 b11011011; 4 d3: result = 7 b11001111; 4 d4: result = 7 b11000110; 4 d5: result = 7 b11101101; 4 d6: result = 17 b1111101; 4 d7: result = 7

4、 b10000111; 4 d8: result = 7 b11101111; 4 d9: result = 7 b11111111; default: result =7 bx; endcase,a,g,d,b,c,f,e,bit7,bit6,bit5,bit4,bit3,bit2,bit1,bit0,g f e d c b a,5.2 case语句举例,reg7:0 ir; casez(ir) 8 b1?: instruction1(ir); 8 b01?: instruction2(ir); 8 b00010?: instruction3(ir); 8 b000001?: instruc

5、tion4(ir); endcase,5.2 case语句举例,reg7:0 ir; casez(ir) 8 b1?: instruction1(ir); 8 b01?: instruction2(ir); 8 b00010?: instruction3(ir); 8 b000001?: instruction4(ir); endcase,5.2 case语句举例,module mux4_to_1 (out, i0, i1, i2, i3, s1, s0); output out; / 根据输入/输出图的端口声明 input i0, i1, i2, i3; input s1, s0; reg

6、out; /把输出变量声明为寄存器类型 /任何输入信号改变，都会引起输出信号的重新计算 /使输出out 重新计算的所有输入信号必须写入 always (.)的变量列表中 always (s1 or s0 or i0 or i1 or i2 or i3) begin case (s1, s0) 2b00: out = i0; 2b01: out = i1; 2b10: out = i2; 2b11: out = i3; default: out = 1bx; endcase end endmodule,if、 case语句正确用法,always (al or d ) / 有锁存器 begin i

7、f ( al ) q = d; end,always (al or d ) / 无锁存器 begin if ( al ) q = d; else q = 0; end,always (sel1:0 or a or b ) case (sel1:0) 2b00:q=a; 2b11:q=b; endcase / 有锁存器,always (sel1:0 or a or b ) case (sel1:0) 2b00:q=a; 2b11:q=b; default:q=1b0; endcase / 无锁存器,5.5 循环语句,5.5 循环语句,5.5 循环语句,parameter size=8,longs

8、ize=16; reg size:1 opa, opb; reg longsize:1 result; begin: mult reg longsize:1 shift_opa, shift_opb； shift_opa = opa; shift_opb = opb; result = 0; repeat(size) begin if(shift_opb1) result = result + shift_opa; shift_opa = shift_opa 1; end end,八位乘法器,5.5 循环语句,5.5 循环语句,5.5 循环语句,5.5 循环语句,parameter size = 8, longsize = 16; regsize:1 opa, opb; reglongsize:1 result; begin:mult integer bindex; result=0; for( bindex=1