通过计数器的值来赋值的问题

querypwr:process(osc_clk)
  begin
    if(osc_clk'event and osc_clk='1')then
        if(pwr_ok='1')then
           count_for_pwr_alternation<=20;
      elsif(count_for_pwr_alternation>0)then
count_for_pwr_alternation<=count_for_pwr_alternation-1;
      end if;
    end if;
end process querypwr;

switchpwr:process(count_for_pwr_alternation)
  begin
    if(count_for_pwr_alternation=0)then
      pwr_switch<='0';
    elsif(count_for_pwr_alternation=20)then
      pwr_switch<='1';
    end if;
end process switchpwr;

这几句程序会出现warning：Too many clocks (> 8) for set/reset analysis of pwr_switch, try moving enabling expressions outside process，
如何达到我的目的并且避免这种warning呢

[编辑 -  2/26/04 by  dswei]

[编辑 -  2/26/04 by  dswei]

switchpwr:process(count_for_pwr_alternation)

敏感信号count_for_pwr_alternation改为cp.


[编辑 -  2/27/04 by  link_bridge]