如何实现单片机与CPLD通讯

Question

单片机为P89V51RD2,CPLD为ATF1508AS,现在要实现单片机与CPLD的通讯，如何实现?希望能讲清原理和用VHDL语言实现,谢谢

Answer 1

1。可以用CPLD模拟一个RS232串口，利用这个串口与单片机通信

下面是用VHDL写的一个串口程序，你可以根据你的通信协议对这个程序略作修改即可使用

-- 本模块的功能是验证实现基本的串口通信的功能。
--
-- 程序实现了一个收发一帧10个bit（即无奇偶校验位）的串口控
--制器，10个bit是1位起始位，8个数据位，1个结束
--位。串口的波特律由程序中定义的div_par参数决定，更改该参数可以实
--现相应的波特率。程序当前设定的div_par 的值是0x104，对应的波特率是
--9600。用一个8倍波特率的时钟将发送或接受每一位bit的周期时间
--划分为8个时隙以使通信同步.
：串口处于全双工工作状态，
--字符串（串口调试工具设成按ASCII码接受方式）；
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

ENTITY UART IS
PORT (
clk : IN std_logic;
rst : IN std_logic;
rxd : IN std_logic; --串行数据接收端
txd : OUT std_logic; --串行数据发送端
en : OUT std_logic; -- 数码管使能
seg_data : OUT std_logic_vector(7 DOWNTO 0); --数码管数据
key_input : IN std_logic --按键输入
);
END UART;

ARCHITECTURE arch OF UART IS

--//////////////////inner reg////////////////////
SIGNAL div_reg : std_logic_vector(15 DOWNTO 0);--分频计数器，分频值由波特率决定。分频后得到频率8倍波特率的时钟
SIGNAL div8_tras_reg : std_logic_vector(2 DOWNTO 0);--该寄存器的计数值对应发送时当前位于的时隙数
SIGNAL div8_rec_reg : std_logic_vector(2 DOWNTO 0); --寄存器的计数值对应接收时当前位于的时隙数
SIGNAL state_tras : std_logic_vector(3 DOWNTO 0); -- 发送状态寄存器
SIGNAL state_rec : std_logic_vector(3 DOWNTO 0); -- 接受状态寄存器
SIGNAL clkbaud_tras : std_logic; --以波特率为频率的发送使能信号
SIGNAL clkbaud_rec : std_logic; --以波特率为频率的接受使能信号
SIGNAL clkbaud8x : std_logic; --以8倍波特率为频率的时钟，它的作用是将发送或接受一个bit的时钟周期分为8个时隙
SIGNAL recstart : std_logic; -- 开始发送标志
SIGNAL recstart_tmp : std_logic; --开始接受标志
SIGNAL trasstart : std_logic;
SIGNAL rxd_reg1 : std_logic; --接收寄存器1
SIGNAL rxd_reg2 : std_logic; --接收寄存器2，因为接收数据为异步信号，故用两级缓存
SIGNAL txd_reg : std_logic; --发送寄存器
SIGNAL rxd_buf : std_logic_vector(7 DOWNTO 0);--接受数据缓存
SIGNAL txd_buf : std_logic_vector(7 DOWNTO 0);--发送数据缓存
SIGNAL send_state : std_logic_vector(2 DOWNTO 0);--每次按键给PC发送"Welcome"字符串，这是发送状态寄存器
SIGNAL cnt_delay : std_logic_vector(19 DOWNTO 0);--延时去抖计数器
SIGNAL start_delaycnt : std_logic; --开始延时计数标志
SIGNAL key_entry1 : std_logic; --确定有键按下标志
SIGNAL key_entry2 : std_logic; --确定有键按下标志
--//////////////////////////////////////////////
CONSTANT div_par : std_logic_vector(15 DOWNTO 0) := "0000000100000100";
--分频参数，其值由对应的波特率计算而得，按此参数分频的时钟频率是波倍特率的8倍，此处值对应9600的波特率，即分频出的时钟频率是9600*8
SIGNAL txd_xhdl3 : std_logic;

BEGIN
en <='0' ;--7段数码管使能信号赋值
txd <= txd_xhdl3;
txd_xhdl3 <= txd_reg ;

PROCESS(clk,rst)
BEGIN

IF (NOT rst = '1') THEN
cnt_delay <= "00000000000000000000";
start_delaycnt <= '0';
ELSIF(clk'EVENT AND clk='1')THEN
IF (start_delaycnt = '1') THEN
IF (cnt_delay /= "11000011010100000000") THEN
cnt_delay <= cnt_delay + "00000000000000000001";
ELSE
cnt_delay <= "00000000000000000000";
start_delaycnt <= '0';
END IF;
ELSE
IF ((NOT key_input='1') AND (cnt_delay = "00000000000000000000")) THEN
start_delaycnt <= '1';
END IF;
END IF;
END IF;
END PROCESS;

PROCESS(clk,rst)
BEGIN

IF (NOT rst = '1') THEN
key_entry1 <= '0';
ELSIF(clk'EVENT AND clk='1')THEN
IF (key_entry2 = '1') THEN
key_entry1 <= '0';
ELSE
IF (cnt_delay = "11000011010100000000") THEN
IF (NOT key_input = '1') THEN
key_entry1 <= '1';
END IF;
END IF;
END IF;
END IF;
END PROCESS;

PROCESS(clk,rst)
BEGIN

IF (NOT rst = '1') THEN
div_reg <= "0000000000000000";
ELSIF(clk'EVENT AND clk='1')THEN
IF (div_reg = div_par - "0000000000000001") THEN
div_reg <= "0000000000000000";
ELSE
div_reg <= div_reg + "0000000000000001";
END IF;
END IF;
END PROCESS;

PROCESS(clk,rst) --分频得到8倍波特率的时钟
BEGIN

IF (NOT rst = '1') THEN
clkbaud8x <= '0';
ELSIF(clk'EVENT AND clk='1')THEN
IF (div_reg = div_par - "0000000000000001") THEN
clkbaud8x <= NOT clkbaud8x;
END IF;
END IF;
END PROCESS;

PROCESS(clkbaud8x,rst)
BEGIN
IF (NOT rst = '1') THEN
div8_rec_reg <= "000";
ELSE IF(clkbaud8x'EVENT AND clkbaud8x = '1') THEN
IF (recstart = '1') THEN --接收开始标志
div8_rec_reg <= div8_rec_reg + "001";--接收开始后，时隙数在8倍波特率的时钟下加1循环
END IF;
END IF;
END IF;
END PROCESS;

PROCESS(clkbaud8x,rst)
BEGIN
IF (NOT rst = '1') THEN
div8_tras_reg <= "000";
ELSE IF(clkbaud8x'EVENT AND clkbaud8x = '1') THEN
IF (trasstart = '1') THEN
div8_tras_reg <= div8_tras_reg + "001";--发送开始后，时隙数在8倍波特率的时钟下加1循环
END IF;
END IF;
END IF;
END PROCESS;

PROCESS(div8_rec_reg)
BEGIN
IF (div8_rec_reg = "111") THEN
clkbaud_rec <= '1'; ---在第7个时隙，接收使能信号有效，将数据打入
ELSE
clkbaud_rec <= '0';
END IF;
END PROCESS;

PROCESS(div8_tras_reg)
BEGIN
IF (div8_tras_reg = "111") THEN
clkbaud_tras <= '1'; --在第7个时隙，发送使能信号有效，将数据发出
ELSE
clkbaud_tras <= '0';
END IF;
END PROCESS;

PROCESS(clkbaud8x,rst)
BEGIN
IF (NOT rst = '1') THEN
txd_reg <= '1';
trasstart <= '0';
txd_buf <= "00000000";
state_tras <= "0000";
send_state <= "000";
key_entry2 <= '0';
ELSE IF(clkbaud8x'EVENT AND clkbaud8x = '1') THEN
IF (NOT key_entry2 = '1') THEN
IF (key_entry1 = '1') THEN
key_entry2 <= '1';
txd_buf <= "01110111"; --"w"
END IF;
ELSE
CASE state_tras IS
WHEN "0000" => --发送起始位
IF ((NOT trasstart='1') AND (send_state < "111") ) THEN
trasstart <= '1';
ELSE
IF (send_state < "111") THEN
IF (clkbaud_tras = '1') THEN
txd_reg <= '0';
state_tras <= state_tras + "0001";
END IF;
ELSE
key_entry2 <= '0';
state_tras <= "0000";
END IF;
END IF;
WHEN "0001" => --发送第1位
IF (clkbaud_tras = '1') THEN
txd_reg <= txd_buf(0);
txd_buf(6 DOWNTO 0) <= txd_buf(7 DOWNTO 1);
state_tras <= state_tras + "0001";
END IF;
WHEN "0010" => --发送第2位
IF (clkbaud_tras = '1') THEN
txd_reg <= txd_buf(0);
txd_buf(6 DOWNTO 0) <= txd_buf(7 DOWNTO 1);
state_tras <= state_tras + "0001";
END IF;
WHEN "0011" => --发送第3位
IF (clkbaud_tras = '1') THEN
txd_reg <= txd_buf(0);
txd_buf(6 DOWNTO 0) <= txd_buf(7 DOWNTO 1);
state_tras <= state_tras + "0001";
END IF;
WHEN "0100" => --发送第4位
IF (clkbaud_tras = '1') THEN
txd_reg <= txd_buf(0);
txd_buf(6 DOWNTO 0) <= txd_buf(7 DOWNTO 1);
state_tras <= state_tras + "0001";
END IF;
WHEN "0101" => --发送第5位
IF (clkbaud_tras = '1') THEN
txd_reg <= txd_buf(0);
txd_buf(6 DOWNTO 0) <= txd_buf(7 DOWNTO 1);
state_tras <= state_tras + "0001";
END IF;
WHEN "0110" => --发送第6位
IF (clkbaud_tras = '1') THEN
txd_reg <= txd_buf(0);
txd_buf(6 DOWNTO 0) <= txd_buf(7 DOWNTO 1);
state_tras <= state_tras + "0001";
END IF;
WHEN "0111" => --发送第7位
IF (clkbaud_tras = '1') THEN
txd_reg <= txd_buf(0);
txd_buf(6 DOWNTO 0) <= txd_buf(7 DOWNTO 1);
state_tras <= state_tras + "0001";
END IF;
WHEN "1000" => --发送第8位
IF (clkbaud_tras = '1') THEN
txd_reg <= txd_buf(0);
txd_buf(6 DOWNTO 0) <= txd_buf(7 DOWNTO 1);
state_tras <= state_tras + "0001";
END IF;
WHEN "1001" => --发送停止位
IF (clkbaud_tras = '1') THEN
txd_reg <= '1';
txd_buf <= "01010101";
state_tras <= state_tras + "0001";
END IF;
WHEN "1111" =>
IF (clkbaud_tras = '1') THEN
state_tras <= state_tras + "0001";
send_state <= send_state + "001";
trasstart <= '0';
CASE send_state IS
WHEN "000" =>
txd_buf <= "01100101"; --"e"
WHEN "001" =>
txd_buf <= "01101100"; --"l"
WHEN "010" =>
txd_buf <= "01100011"; --"c"
WHEN "011" =>
txd_buf <= "01101111"; --"o"
WHEN "100" =>
txd_buf <= "01101101"; --"m"
WHEN "101" =>
txd_buf <= "01100101";-- "e"
WHEN OTHERS =>
txd_buf <= "00000000";

END CASE;
END IF;
WHEN OTHERS =>
IF (clkbaud_tras = '1') THEN
state_tras <= state_tras + "0001";
trasstart <= '1';
END IF;

END CASE;
END IF;
END IF;
END IF;
END PROCESS;

PROCESS(clkbaud8x,rst) --接受PC机的数据
BEGIN
IF (NOT rst = '1') THEN
rxd_reg1 <= '0';
rxd_reg2 <= '0';
rxd_buf <= "00000000";
state_rec <= "0000";
recstart <= '0';
recstart_tmp <= '0';
ELSE IF(clkbaud8x'EVENT AND clkbaud8x = '1') THEN
rxd_reg1 <= rxd;
rxd_reg2 <= rxd_reg1;
IF (state_rec = "0000") THEN
IF (recstart_tmp = '1') THEN
recstart <= '1';
recstart_tmp <= '0';
state_rec <= state_rec + "0001";
ELSE
IF ((NOT rxd_reg1 AND rxd_reg2) = '1') THEN --检测到起始位的下降沿，进入接受状态
recstart_tmp <= '1';
END IF;
END IF;
ELSE
IF (state_rec >= "0001" AND state_rec<="1000") THEN
IF (clkbaud_rec = '1') THEN
rxd_buf(7) <= rxd_reg2;
rxd_buf(6 DOWNTO 0) <= rxd_buf(7 DOWNTO 1);
state_rec <= state_rec + "0001";
END IF;
ELSE
IF (state_rec = "1001") THEN
IF (clkbaud_rec = '1') THEN
state_rec <= "0000";
recstart <= '0';
END IF;
END IF;
END IF;
END IF;
END IF;
END IF;
END PROCESS;

PROCESS(rxd_buf) --将接受的数据用数码管显示出来
BEGIN
CASE rxd_buf IS
WHEN "00110000" =>
seg_data <= "00000011";
WHEN "00110001" =>
seg_data <= "10011111";
WHEN "00110010" =>
seg_data <= "00100101";
WHEN "00110011" =>
seg_data <= "00001101";
WHEN "00110100" =>
seg_data <= "10011001";
WHEN "00110101" =>
seg_data <= "01001001";
WHEN "00110110" =>
seg_data <= "01000001";
WHEN "00110111" =>
seg_data <= "00011111";
WHEN "00111000" =>
seg_data <= "00000001";
WHEN "01000001" =>
seg_data <= "00011001";
WHEN "01000010" =>
seg_data <= "00010001";
WHEN "01000011" =>
seg_data <= "11000001";
WHEN "01000100" =>
seg_data <= "01100011";
WHEN "01000101" =>
seg_data <= "10000101";
WHEN "01000110" =>
seg_data <= "01100001";
WHEN "01000111" =>
seg_data <= "01110001";
WHEN OTHERS =>
seg_data <= "11111111";

END CASE;
END PROCESS;

END arch;
2。可利用单片机的IO口与CPLD实现通信，其他人已经回答过了，我不再赘述。

Answer 2

有以下几种办法：
1.使用8951的外部寻址方式，将单片机的数据总线 部分地址总线和控制总线连接到CPLD 然后再CPLD里根据单片机的外部寻址时序读取数据，这种方式CPLD处理最简单，速度最快。但缺点是需要连接的线很多
2.串行方式通信：这个和协议有关系，选一种比较好的推荐一下
1）普通的UART那种串行通信方式一个起始位 8位数据位 一个结束位 CPLD检测到下降沿认为新的数据到来，然后开始将端口的数据读入 当然波特率要你自己来定
2）SPI 方式 这需要单片机测用端口模拟 两个数据线 一个时钟线
CPLD只要检测到上升沿就开始读入数据
UART方式简单 因为51单片机内部本身就集成了串行通讯的外设 但SPI通信速度快
希望对你有帮助！

Answer 3

最简单是用CPLD 模拟一个SPI接口，协议也比较简单，3跟线就好了（一根片选CS,一根数据输入DI，一根数据输出DO），再定义几个命令就好了。如果楼主了解I2C协议更好，只需两根线就好了。

Answer 4

关键在通讯协议上，看你怎么定义了，简单的cpld检测单片机高低电平也是通讯。

Answer 5

并行、IIC、UART、SPI，看你硬件资源、协议熟练程度和项目要求了。