1、占空比50%时钟产生     

always
begin<clock>    =    1'b0    ;#<PERIOD/2>    ;<clock>    =    1'b1    ;#<PERIOD/2>    ;
end

    reg <clock> = 1'b0    ;alwaysbegin#<PERIOD/2>    ;<clock>    =    ~<clock>    ;end    

2、高低电平参数时钟产生   

always
begin<clock>    =    1'b0    ;#<LOW_TIME>    ;<clock>    =    1'b1    ;#<HIGH_TIME>    ;
end

3、占空比可调clk 

always
begin<clock>    =    1'b0    ;#( <PERIOD> - (<PERIOD>*<DUTY_CYCLE>) )    ;<clock>    =    1'b1    ;#( <PERIOD> - <DUTY_CYCLE> )    ;
end    

4、差分时钟

always
beginclk_p    =    1'b0    ;clk_n    =    1'b1    ;#30    ;clk_p    =    1'b1    ;clk_n    =    1'b0    ;#30    ;end