Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Problem with declaring inout port in code

Status
Not open for further replies.
R

Ravindranit

Newbie level 2
Joined
Jun 11, 2008
Messages
2
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,296
problem inout port

Hello friends,
I want to use inout declaration in my code. but it gives the error that port is not a legal value. i use it into the always block both as a input & output.
code is:


module check(a,s1,out,d,enable);
input s1,enable;
input a;
output out;
reg b;
inout d;
reg out;
assign b=d;
always @(posedge enable)
if(s1)
begin out=a; d=~a; end
else
out=b;
endmodule
 

Re: problem inout port

The code is syntactical correct when you specify reg d and omit reg b.
However, reading the from bidirectional pin requires setting the output to 'Z' before.

I have code as shown below for similar purposes.

Code: 
input FPGA_nRD,
input FPGA_nWR,
input [6:0] FPGA_A,
inout [15:0] FPGA_DB,

reg [15:0] FPGA_RDDATA;

assign FPGA_DB = (FPGA_nRD)? 16'hZZZZ : FPGA_RDDATA;
 

Re: problem inout port

module check(a,s1,out,d,enable);

input s1,enable;
input a;
output out;
inout d;

wire b;
wire d;
reg out;

assign b = d;
assign d = (enable & s1) ? ~a : 1'bz;

always @ *
if (s1 & enable)
out = a;
else
out = b;

endmodule
 

Re: problem inout port

thank you for your help....
i am also facing problem to write the test bsnch of the above code. it give me error on declaration of inout port type ( reg or wire). if i am taking reg it gives eroor " net is not a legal value".
and when i take it as a wire it does take any input from it................
please help me.........
 

problem inout port

From my experience, i never use directly inout port, bidirectional data port fall in either 1 of 2 categories : (1) Digital feedback or (2) Interconnections. In both 2 case you can convert the bidirectional data port into uni-directional data port. Say 1 inout port can be seperated into 2 unidirectional dta ports, 1 input and 1 output port. The bidirection is applied when you manually port map these 2 ports together...
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top