Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
13 years ago

Creating a bidirectional bus

I want to connect a USB chip (FT245R) to a CPLD. To do that I need a bidirectional 8-bit bus. I thought I could declare the pins to be bidirectional and with a mux, read to or write from the pins as ...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
13 years ago

inbus was declared as a wire, it is the input to another module.

With the changes below indicated by "<<<<" full compilation was successful. I haven't test it... 


wire  USBBUS_i;
reg  USBBUS_o;
reg USBBUS_oe;
assign USBBUS_i = USBBUS;
assign USBBUS = USBBUS_oe == 1'b1 ? USBBUS_o : 8'hzz;
 
wire  inbus_w;
reg  inbus_r;
 
assign inbus_w = inbus;     // <<<<
assign inbus = inbus_r;     // <<<<
always @(negedge clk) begin
    if(TXE == 0) begin
        USBBUS_o <= outbus;
        USBBUS_oe <= 1'b1;
    end
    else begin
        USBBUS_o <= 8'hxx;
        USBBUS_oe <= 1'b0;
    end
    if (RXF == 0) begin
        inbus_r <= inbus;   // <<<<
    end
end