yuenkit
Advanced Member level 4
Code:
module fsm1 (x, clk, rst, y);
input x, clk, rst;
output y;
parameter [3:0]
set0 = 4'b0001, hold0 = 4'b0010, set1 = 4'b0100, hold1 = 4'b1000;
reg [3:0] current_state, next_state;
always @ (posedge clk or posedge rst)
if (rst)
current_state = set0;
else
current_state = next_state;
always @ (current_state or x)
case (current_state)
set0:
next_state = hold0;
hold0:
if (x == 0)
next_state = hold0;
else
next_state = set1;
set1:
next_state = hold1;
hold1:
next_state = set0;
default :
next_state = set0;
endcase
assign y = current_state == hold0 & x;
endmodulePlease look at the last line :
assign y = current_state == hold0 & x;
hold0 is a 4 bit variable with the value 4'b0010, and x is a single bit variable.
when they ANDed together, will it posible to get a TRUE value?
I thought, x will be zero extended to match the length of hold0, which will be 4'b000x, so no matter what x value is, the result is always false.
The above FSM i taken from the DC Presto compiler manual. It seems like the output will be 1 if the x is 1.