求大神帮忙解释一下VHDL串口通信？解说一下每一条语句的意思，真心感谢！

library ieee

useieee.std_logic_1164.all

entity correspondis

port(

clk,en:in std_logic

Send_data:in std_logic_vector(9 downto 0)

serial:out std_logic)

end correspond

architecturecorrespond_arc of correspond is--定义结构体

begin

process(clk)

variable count:integer range 0 to 9 :=0 --定义变量，初值为0

begin

if (en='0') then

--如果信号不允许发送，即EN= ‘0’，则计数0，串口输出高电平‘1’

count:=0

serial<='1'

elsif rising_edge(clk) then

--如果允许发送，即EN= ‘1’，开始发送

if (count=9) then--如果count=9，则不停的发送数据最高位send_data[9]

serial<=Send_data(9)

else--如果count/=9，则依次从0位到9位开始发送数据

serial<=Send_data(count)

count:=count+1

end if

end if

end process

endcorrespond_arc

晕，你这个没有任何的程序描述，纯粹的输入输出

module top_design(vp_in,

vp_out,

VBLK,

FID,

fpga_0_RS232_req_to_send_pin,

fpga_0_RS232_RX_pin,

fpga_0_RS232_TX_pin,

fpga_0_Generic_GPIO_GPIO_d_out_pin, fpga_0_Generic_GPIO_GPIO_in_pin,

fpga_0_Generic_GPIO_GPIO_t_out_pin ,

fpga_0_Generic_GPIO_GPIO_IO_pin_t,

sys_clk_pin,

sys_rst_pin ,

led_0 ,

led_1,

led_2,

led_3,

led_4,

led_5 ,

VPOUT_LLC,

VPIN_LLC,

vblk_t,

avid_t,

vsync_t,

hsync_t,

fid_t,

in_clk_t,

reset_t,

vp_in_t,

IIC_IO_pin)

input [7:0]vp_in

input VBLK

input fpga_0_RS232_RX_pin

input [1:0]fpga_0_Generic_GPIO_GPIO_in_pin

input sys_clk_pin

input sys_rst_pin

input VPIN_LLC

input vblk_t

input avid_t

input vsync_t

input hsync_t

input fid_t

input in_clk_t

input vp_in_t

output [7:0]vp_out

output fpga_0_RS232_req_to_send_pin

output fpga_0_RS232_TX_pin

output [1:0]fpga_0_Generic_GPIO_GPIO_d_out_pin

output [1:0]fpga_0_Generic_GPIO_GPIO_t_out_pin

output led_0

output led_1

output led_2

output led_3

output led_4

output led_5

output VPOUT_LLC

output reset_t

inout [1:0]fpga_0_Generic_GPIO_GPIO_IO_pin_t

inout [1:0]IIC_IO_pin

end module

你这段VHDL代码只是实体描述部分，具体设计根本就没有，毕业设计根本糊弄不过去

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