strang things about FSM

[Altera_Forum]

in my design i use FSM,and i don't know why my FSM alway be in a undefined status, 

see the picture below,   and I have use "default" : default:begin ............ end

[Altera_Forum]

i guess we need more information how you have designed your fsm. 

do you have more states than the default ? how do you change the fsm state ? is you fsm a meely or a moore state machine ?  could you give us some code snippet ?

[Altera_Forum]

ok ,i upload my code

[Altera_Forum]

i use one-hot

[Altera_Forum]

I found when irq_i is low,then state machine go to 00000h.see picture nether: 

 another question:does "if...else if.....else "have priority level?   code: SPI_IDLE_status:  begin  TXBnCTRL_whetherCanTxNext <= 1'b1;   rxdFIFOHaveFrameIrq <= 1'b1;  SPI_other_CANINTF_irq_reg <= 1'b1;   if(!irq_i)  begin  spiStatusMachineReg <=SPI_CANINTF1;  TXBnCTRL_whetherCanTxNext <= 1'b0;   end  else if(transmitFIFOUsedw>>`wholeFrameLength   begin  TXBnCTRL_whetherCanTxNext <= 1'b0;  txd_FIFO_num_reg <= 15;  spiStatusMachineReg <=SPI_SEND_status;  end  else spiStatusMachineReg <=SPI_IDLE_status;  end

[Altera_Forum]

no. 

if ( is true )  execute this if 1. if is true else otherwise if ( this is true )  execute this if 1. if is false and the second is true else  execure this if none of the if is true  if the first if is true then none of the others are executed

[Altera_Forum]

you a.v is not clearly arranged and so hard so read and understand 

what i do with fsm is that have one always block that handles only the fsm register and no other register.   spiStatusMachineReg is your fsm register  after reset it seems to start with SPI_config_status the next state depends upon "addr" but thats an external signal  have you checked the quartus setting about State machine Processing ?  you don#T need to code one hot shot as quartus can change the fsm type if needed. normaly it is set to one-hot, change it to user encoded so it must keep your coding style. and not modifying it. also signaltap will show you the single states and you can assign names to ist via a table, that makes ist easier to read

[Altera_Forum]

Hello 

 There is one option into quartus that allows you to visualize your Finite State Machines.  Go to   Tools>Netlist viewer>STATE MACHINE VIEWER.  This tool shows very beautifull diagrams of your FSM.   Good Luck.   DABG