我正在尝试为键盘驱动程序编写VHDL代码,因为我需要读取11位向量中的8位,这里要清楚的是读取输入信号的过程(有信号CLK和数据) .
KEYBOARD_SYNC : process(CLK,SYSRESET)
begin
if (CLK'event and CLK='1') then
KEYBOARD_CLK_VECTOR <= KEYBOARD_CLK_VECTOR( 6 downto 0 ) & KEYBOARD_CLK;
RECEIVING_FLAG <='0';
if ( KEYBOARD_CLK_VECTOR = x"F0" ) then -- Falling edge
KEYBOARD_DATA_VECTOR <= KEYBOARD_DATA_VECTOR( 9 downto 0 ) & KEYBOARD_DATA;-- shifting
BIT_COUNTER <= BIT_COUNTER + 1 ;
end if;
if( BIT_COUNTER = 11 ) then
RECEIVING_FLAG <='1';
TEMP_WORD <= KEYBOARD_DATA_VECTOR( 8 downto 1 );
BIT_COUNTER <=0 ;
KEYBOARD_DATA_VECTOR <= (others =>'1');
end if ;
end if ;
end process KEYBOARD_SYNC;
PROCESSING : process ( CLK ,SYSRESET )
begin
if ( CLK'event and CLK ='1') then
if ( RECEIVING_FLAG = '1') then
ACTUAL_WORD <= TEMP_WORD;
end if ;
end if ;
end process PROCESSING;
为了运行模拟,我编写了一个应该发送 0xF0
的测试平台,这个值应该保存在ACTUAL_WORD中,这里应该是测试平台的一部分:
-- Timing variables
constant CLK_PERIOD: time := 10 ns;
constant KEYBOARD_CLK_PERIOD: time := 80 us;
...................................................
KEYBOARD_PROCESS : process
BEGIN
-- BREAK Code
KEYBOARD_CLK <= '1';
KEYBOARD_DATA <= '0';
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '0'; --Start Bit always 0
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '1';
KEYBOARD_DATA <= '1'; -- Sending a break code 0xF0
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '0'; -- 0 Bit
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '1';
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '0'; -- 1 Bit
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '1';
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '0'; -- 2 Bit
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '1';
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '0'; -- 3 Bit
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_DATA<= '0';
KEYBOARD_CLK <= '1';
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '0'; -- 4 Bit
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '1';
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '0'; -- 5 Bit
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '1';
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '0'; -- 6 Bit
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '1';
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '0'; -- 7 Bit
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_DATA<= '1';
KEYBOARD_CLK <= '1';
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '0'; -- Parity Bit
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '1';
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '0'; -- Stop Bit always 1
wait for (KEYBOARD_CLK_PERIOD/2);
KEYBOARD_CLK <= '1';
wait for (KEYBOARD_CLK_PERIOD/2);
end process KEYBOARD_PROCESS;
结果是:
(可点击)
问题是我继续阅读 0xE1
而不是 0xF0
其他一切正常,我可以't figure out why I' m错过这个位 .
1 回答
读取0xF0的周期性模式为0xE1看起来像1位移位,这可能是由同时生成时钟(
KEYBOARD_CLK
)和数据(KEYBOARD_DATA
)的测试平台引起的 .在硬件设计中,输出数据是由时钟产生的,因此在时钟的上升沿和新数据之间至少会有一个增量周期延迟,但当前的测试平台设计会同时生成时钟和数据有:
其波形看起来很熟悉,但信号流实际上缺少时钟和数据之间的增量循环延迟,因此数据比波形预期提前一个周期准备就绪,导致1位移位 . 然而,在当前的波形图中没有示出,这可能是令人费解的部分 . ModelSim可以显示缺少delta周期,但这不是默认值 .
在测试平台设计中遵循通用设计方法通常是一个好主意,以便保持单一的通用设计实践,这使得读取代码和波形更容易 .
因此,在测试平台中,制作一个生成时钟的过程,然后根据时钟进行生成数据的过程,就像硬件设计一样 . 这可以这样做:
根据所需的测试模式调整重复数据的循环 .