FIFO 是FPGA設(shè)計中最有用的模塊之一。FIFO 在模塊之間提供簡單的握手和同步機(jī)制，是設(shè)計人員將數(shù)據(jù)從一個模塊傳輸?shù)搅硪粋€模塊的常用選擇。

在這篇文章中，展示了一個簡單的 RTL 同步 FIFO，可以直接在自己的設(shè)計中配置和使用它，該設(shè)計是完全可綜合的。

為什么要自己設(shè)計FIFO

那么，為什么呢？網(wǎng)上有很多關(guān)于 FIFO 的 Verilog/VHDL 代碼的資源，過去，我自己也使用過其中的一些。但令人沮喪的是，它們中的大多數(shù)都存在問題，尤其是在上溢出和下溢出條件下。所以想一勞永逸地解決這些問題。

FIFO 規(guī)格性能

同步，單時鐘。

基于寄存器的 FIFO，適用于中小型 FIFO。

Full、Empty、Almost-full、Almost-empty 標(biāo)志。

完全可配置的數(shù)據(jù)寬度、深度和標(biāo)志。

完全可綜合的系統(tǒng) Verilog 代碼。

/*===============================================================================================================================
Design:Single-clockSynchronousFIFO

Description:Fullysynthesisable,configurableSingle-clockSynchronousFIFObasedonregisters.
-ConfigurableDatawidth.
-ConfigurableDepth.
-ConfigurableAlmost-fullandAlmost-emptysignals.
===============================================================================================================================*/

modulemy_fifo#(
parameterDATA_W=4,//Datawidth
parameterDEPTH=8,//DepthofFIFO
parameterUPP_TH=4,//UpperthresholdtogenerateAlmost-full
parameterLOW_TH=2//LowerthresholdtogenerateAlmost-empty
)

(
inputclk,//Clock
inputrstn,//Active-lowSynchronousReset

inputi_wren,//WriteEnable
input[DATA_W-1:0]i_wrdata,//Write-data
outputo_alm_full,//Almost-fullsignal
outputo_full,//Fullsignal

inputi_rden,//ReadEnable
output[DATA_W-1:0]o_rddata,//Read-data
outputo_alm_empty,//Almost-emptysignal
outputo_empty//Emptysignal
);


/*-------------------------------------------------------------------------------------------------------------------------------
InternalRegisters/Signals
-------------------------------------------------------------------------------------------------------------------------------*/

logic[DATA_W-1:0]data_rg[DEPTH];//Dataarray
logic[$clog2(DEPTH)-1:0]wrptr_rg;//Writepointer
logic[$clog2(DEPTH)-1:0]rdptr_rg;//Readpointer
logic[$clog2(DEPTH):0]dcount_rg;//Datacounter

logicwren_s;//WriteEnablesignalgeneratediffFIFOisnotfull
logicrden_s;//ReadEnablesignalgeneratediffFIFOisnotempty
logicfull_s;//Fullsignal
logicempty_s;//Emptysignal


/*-------------------------------------------------------------------------------------------------------------------------------
SynchronouslogictowritetoandreadfromFIFO
-------------------------------------------------------------------------------------------------------------------------------*/
always@(posedgeclk)begin

if(!rstn)begin

data_rg<=?'{default:?'0}?;
??????wrptr_rg??<=?0??????????????;
??????rdptr_rg??<=?0??????????????;??????
??????dcount_rg?<=?0??????????????;

???end

???else?begin

??????ready_rg?<=?1'b1?;
??????
??????/*?FIFO?write?logic?*/????????????
??????if?(wren_s)?begin??????????????????????????
?????????
?????????data_rg?[wrptr_rg]?<=?i_wrdata?;????????//?Data?written?to?FIFO

?????????if?(wrptr_rg?==?DEPTH?-?1)?begin
????????????wrptr_rg?<=?0???????????????;????????//?Reset?write?pointer??
?????????end

?????????else?begin
????????????wrptr_rg?<=?wrptr_rg?+?1????;????????//?Increment?write?pointer????????????
?????????end

??????end

??????/*?FIFO?read?logic?*/
??????if?(rden_s)?begin?????????

?????????if?(rdptr_rg?==?DEPTH?-?1)?begin
????????????rdptr_rg?<=?0???????????????;????????//?Reset?read?pointer
?????????end

?????????else?begin
????????????rdptr_rg?<=?rdptr_rg?+?1????;????????//?Increment?read?pointer????????????
?????????end

??????end

??????/*?FIFO?data?counter?update?logic?*/
??????if?(wren_s?&&?!rden_s)?begin???????????????//?Write?operation
?????????dcount_rg?<=?dcount_rg?+?1?;
??????end????????????????????
??????else?if?(!wren_s?&&?rden_s)?begin??????????//?Read?operation
?????????dcount_rg?<=?dcount_rg?-?1?;?????????
??????end

???end

end


/*-------------------------------------------------------------------------------------------------------------------------------
???Continuous?Assignments
-------------------------------------------------------------------------------------------------------------------------------*/

//?Full?and?Empty?internal
assign?full_s??????=?(dcount_rg?==?DEPTH)???1'b1?:?0?;
assign?empty_s?????=?(dcount_rg?==?0????)???1'b1?:?0?;

//?Write?and?Read?Enables?internal
assign?wren_s??????=?i_wren?&?!full_s????????????????;??
assign?rden_s??????=?i_rden?&?!empty_s???????????????;

//?Full?and?Empty?to?output
assign?o_full??????=?full_s??????????????????????????;
assign?o_empty?????=?empty_s?????????????????????????;

//?Almost-full?and?Almost?Empty?to?output
assign?o_alm_full??=?(dcount_rg?>UPP_TH)?1'b1:0;
assigno_alm_empty=(dcount_rg

	

	基于 RAM 的 FIFO

	在上面的步驟中，我們看到了一個基于寄存器的同步FIFO。接下來，我們來看看基于 RAM 的 FIFO。該 FIFO 在 RAM 而不是寄存器上實現(xiàn)其數(shù)據(jù)陣列。這適用于在硬件上實現(xiàn)大型 FIFO ；特別是在 FPGA 上，F(xiàn)PGA 里有大量的Block RAM 可用。這將降低資源利用率，也可以獲得更好的時序性能。

	詳細(xì)代碼：

	?

	https://github.com/iammituraj/FIFOs

	    責(zé)任編輯：彭菁