recieve.tdf

在QuartusII中使用AHDL语言编写一个RS232串行数据通信接口

subdesign 'UART'
% ***** Clock frequency is 3.456 MHz ***** %
% ***** Clock period is 289.35 ns ***** %
% ***** Data rate is 28,800 bps ***** %
% ***** DataIn period is 34.72 us ***** %
(
	Clock,DataIn               :Input;
	PosEdge                    :output;
	DataDelay[1..0]            :output;
	SampleCount[6..0],BitEdge  :output;
	InRegister[7..0]           :output;
	SampleCountReset           :output;
	Receiving,BitCounter[3..0] :Output;
	StopReceiving              :output;
	BitClock                   :output;
)
Variable
	DataDelay[1..0]           :DFF;
	Receiving                 :DFF;
	InRegister[7..0]          :DFF;
	SampleCount[6..0]         :DFF;
	SampleCountReset          :DFF;
	BitCounter[3..0]          :DFF;
	BitClock                  :DFF;
	StopReceiving             :DFF;

Begin
	%***** Connect Clocks *****%
	DataDelay[1..0].clk=Clock;
	SampleCount[].clk=Clock;
	InRegister[].clk=BitClock;
	SampleCountReset.clk=Clock;
	Receiving.clk=Clock;
	StopReceiving.clk=Clock;
	BitCounter[].clk=BitClock;
	BitClock.clk=BitEdge;

	%***** Connect Input Data Line *****%
	DataDelay[1].d=DataIn;
	InRegister[7].d=DataIn;
	InRegister[6..0].d=InRegister[7..1].q;

	%***** Perfoorm Edge Detection *****%
	DataDelay[0].d=DataDelay[1].q;
	PosEdge=DataDelay[1]&!DataDelay[0];
	
	%***** Set the Reciving Signle *****%
	Receiving.d=PosEdge#Receiving.q&!StopReceiving;

	%***** Generate BitEdge Pulse *****%
	if(Receiving)then
       SampleCount[].d=(SampleCount[].q+1)&!SampleCountReset;
             Case SampleCount[] is
                    WHEN H"3C" =>
                        BitEdge=Vcc;
                        SampleCountReset.d=Vcc;
                    WHEN OTHERS =>
                         BitEdge=Gnd;
                        SampleCountReset.d=Gnd;
             End Case;
	end if;
	
	%***** Centers and edges *****%
	BitClock.d=!BitClock.q;
	BitClock.clrn=Receiving;

	%***** Increment Bit Counter *****%
	BitCounter[].d=BitCounter[]+1;
	BitCounter[].clrn=Receiving;

	%***** Set end of data word *****%
	if (BItCounter[]==H"9") Then
        StopReceiving.d=Vcc;
	else
        StopReceiving.d=Gnd;
	end if;                      

End;