I am New to Verilog, I am trying to make a CPLD power up protection logic, it actually use a bunch of Timer to validate the state machine. I have a CPLD with 1Mhz OSC, and I am trying to make a 15s timer, I figure the code, but it have compile error, says "cannot be assigned more than one value". I knew this mean the signal net has been control by two different signal, but it has a error line shows
Error (12014): Net "Fifty_m_second_Devide_Clock_input", which fans out to "Timer[0]", cannot be assigned more than one value Error (12015): Net is fed by "clk_div:d|clk_out" Error (12015): Net is fed by "Fifty_m_second_Devide_Clock_input"
why "Fifty_m_second_Devide_Clock_input" is connected to itself??
module PowerUpProtection(
//---------------------------------------------------------------------------
// Inputs
//---------------------------------------------------------------------------
input wire Fifty_m_second_Devide_Clock_input,
input wire Clock,
input wire Reset,
input wire Input1_Check_precharge_status,
input wire Input2_MainPowerSwitch_relay_status_Check,
input wire Input3_powerUp_validation,
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
// Outputs
//---------------------------------------------------------------------------
output reg Output1_Relay_Swtich_For_Main_PowerSource,
output reg Output2_Switch_On_and_Charge_CAP,
output reg Output3_Switch_On_and_power_SoM,
output reg Output4_Press_and_hold_the_powerSource,
output reg Output5_Switch_on_relay_when_CPLD_powerup
//---------------------------------------------------------------------------
);
// this is a Module Instantiation, connect the inputs and output from different module within CPLD.
clk_div d(
.Clock (Clock),
.reset(Reset),
.clk_out(Fifty_m_second_Devide_Clock_input)
);
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
// State Encoding
//---------------------------------------------------------------------------
localparam STATE_0_Initial = 4'd0,
STATE_1_Press_and_hold = 4'd1,
STATE_2_Power_up = 4'd2,
STATE_3_Check_Switches = 4'd3,
STATE_4_SwtichSafe_StartPreCharging = 4'd4,
STATE_5_ERROR = 4'd5,
STATE_6_CAP_is_Charging = 4'd6,
STATE_7_Charging_End_SwitchOn_MainPower = 4'd7,
STATE_8_PowerSupply_Ready = 4'd8,
ERROR_9_TIME_OUT = 4'd9,
STATE_10_Precharge_Switch_is_broken = 4'd10,
STATE_11_Main_power_switch_is_broken = 4'd11,
STATE_12_Both_switches_are_broken = 4'd12,
STATE_13_PlaceHolder = 4'd13,
STATE_14_PlaceHolder = 4'd14,
STATE_15_PlaceHolder = 4'd15;
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
// State reg Declarations
//---------------------------------------------------------------------------
reg [3:0] CurrentState = 4'd0;
reg [3:0] NextState = 4'd0;
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
// Timer reg Declarations
//---------------------------------------------------------------------------
reg [8:0] Timer = 0;
reg enable_the_counter = 0; // the boolean to enbale the counter.
reg clear_the_counter = 0;
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
// Outputs
//---------------------------------------------------------------------------
always@(*) begin
// clear for the initial state.
reg Output1_Relay_Swtich_For_Main_PowerSource = 0;
reg Output2_Switch_On_and_Charge_CAP = 0;
reg Output3_Switch_On_and_power_SoM = 0;
reg Output4_Press_and_hold_the_powerSource = 0;
reg Output5_Switch_on_relay_when_CPLD_powerup = 0;
case (CurrentState)
STATE_1_Press_and_hold : begin
Output4_Press_and_hold_the_powerSource = 1;
end
STATE_2_Power_up : begin
Output5_Switch_on_relay_when_CPLD_powerup = 1;
end
STATE_3_Check_Switches : begin
Output2_Switch_On_and_Charge_CAP = 1;
end
STATE_4_SwtichSafe_StartPreCharging : begin
Output2_Switch_On_and_Charge_CAP = 1;
end
STATE_5_ERROR : begin
// to be determined
end
STATE_6_CAP_is_Charging : begin
// wait for the charging to be complete
end
STATE_7_Charging_End_SwitchOn_MainPower : begin
Output1_Relay_Swtich_For_Main_PowerSource =1;
end
STATE_8_PowerSupply_Ready : begin
Output5_Switch_on_relay_when_CPLD_powerup = 0;
Output3_Switch_On_and_power_SoM = 1;
end
endcase
end
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
// Synchronous State-Transition always@(posedge Clock) block
//---------------------------------------------------------------------------
always@(posedge Clock) begin
if (Reset) CurrentState <= STATE_0_Initial;
else CurrentState <= NextState;
end
//---------------------------------------------------------------------------
//---------------------------------------------------------------------------
// conditional State-Trasnsition Always@(*) block
//---------------------------------------------------------------------------
always@(*) begin
NextState = CurrentState;
case (CurrentState)
STATE_0_Initial :begin
NextState = STATE_1_Press_and_hold;
end
STATE_1_Press_and_hold : begin
if (Input3_powerUp_validation) NextState = STATE_2_Power_up;
end
STATE_2_Power_up : begin
if (Input3_powerUp_validation) NextState = STATE_3_Check_Switches;
end
STATE_3_Check_Switches : begin
if (Input1_Check_precharge_status == 0 && Input2_MainPowerSwitch_relay_status_Check == 1 )
begin
NextState = STATE_4_SwtichSafe_StartPreCharging;
enable_the_counter = 1; //Start to count the time.
end
else if (Input1_Check_precharge_status == 1 && Input2_MainPowerSwitch_relay_status_Check == 1)
begin
NextState = STATE_10_Precharge_Switch_is_broken;
end
else if (Input1_Check_precharge_status == 0 && Input2_MainPowerSwitch_relay_status_Check == 0)
begin
NextState = STATE_11_Main_power_switch_is_broken;
end
else
begin
NextState = STATE_12_Both_switches_are_broken;
end
end
STATE_4_SwtichSafe_StartPreCharging : begin
if (Input1_Check_precharge_status == 1 && Timer <= 300) //equals to 15 seconds
NextState = STATE_6_CAP_is_Charging;
else if (Timer > 300)
NextState = STATE_5_ERROR; //Time out Error
clear_the_counter = 1;
enable_the_counter = 0;
end
STATE_6_CAP_is_Charging : begin
if (Input1_Check_precharge_status == 0 && Timer <= 300)
begin
NextState = STATE_7_Charging_End_SwitchOn_MainPower;
clear_the_counter = 1; // timer is over, clear the counter.
enable_the_counter =0;
end
else if (Timer > 300)
begin
NextState = STATE_5_ERROR; //Time out Error
clear_the_counter = 1;
enable_the_counter = 0;
end
end
STATE_7_Charging_End_SwitchOn_MainPower : begin
//enable the counter again, and count for 50 m seconds.
enable_the_counter = 1;
if (Input2_MainPowerSwitch_relay_status_Check ==1)
begin
if (Timer <=1)
NextState = STATE_7_Charging_End_SwitchOn_MainPower; // if time is not 50 ms yet, go back to itself current state
else
NextState = STATE_5_ERROR; //Time out Error
clear_the_counter = 1;
enable_the_counter = 0;
end
else if (Input2_MainPowerSwitch_relay_status_Check == 0) // if the switch is ready right away, that is best.
begin
NextState = STATE_8_PowerSupply_Ready;
end
else
NextState = STATE_5_ERROR; //Time out Error
clear_the_counter = 1;
enable_the_counter = 0;
end
//---------------------------------------------------------------------------
// Place-Holder transition.
//---------------------------------------------------------------------------
STATE_13_PlaceHolder : begin
NextState = STATE_5_ERROR;
end
STATE_14_PlaceHolder : begin
NextState = STATE_5_ERROR;
end
STATE_15_PlaceHolder : begin
NextState = STATE_5_ERROR;
end
endcase
end
//---------------------------------------------------------------------------
// 50 m Seconds counter block, make the osc into 20 HZ by implement the counter
//---------------------------------------------------------------------------
always@(posedge Fifty_m_second_Devide_Clock_input or posedge Reset or posedge clear_the_counter ) begin
if (Reset == 1 || clear_the_counter == 1)
begin
Timer = 0;
end
else
begin
if (enable_the_counter)
Timer <= Timer + 1'b1;
end
end
//---------------------------------------------------------------------------
endmodule
//clock devider, the board has a 10 M hz osc,
//so I create this code to count 200000 times
//for each posedge and that equalle to 50 m-second.
// if count until 50 m-second, this clk_out will output one positive edge.
module clk_div(
input Clock,
input reset,
output reg clk_out
);
parameter diver = 99999;
reg [23:0] count;//just for 99999 or warning
always@(posedge Clock or posedge reset)
begin
if(reset)
begin
count <= 0;
clk_out <= 1'b0;
end
else if(count == diver)
begin
clk_out <= ~clk_out;
count <= 0;
end
else
begin
count <= count + 1'b1;
end
end
endmodule
