我不用根据板子的时钟50MHz,利用循环叠加出,我想得到的秒数if rising_edge(clk) then
-- Generate a start stobe every 1 msec to start
-- A/D conversion. The pulse width of the start
-- strobe is 1 usec
cntr := cntr + 1;
if (cntr = 50000) then
start_strobe <= '1';
elsif (cntr = 50050) then
cntr := 0;
start_strobe <= '0';
end if;