Moving code to different module causes error ??? :(

[Davidg]

If I un-comment the peice of code below, it all compiles. If it is as
below (commented out)in this module, and I place that peice of code in
a different module, the compiler says that Tri-State buffer 'AD' will
be permanently disabled. Any suggestions why this happens? Very
frustating for us nubees
All help will be appreciated.

module Decode
(

A, RD, WR, PSEN, AD,FLASH_SEL,BRK_SEL,
BRK_PAGE,RAM_PAGE,RAM_SEL,ALE,RESET

);
// Port Declaration


input [15:8] A;
inout [7:0] AD;
input RD;
input WR;
input PSEN;
input ALE;
input RESET;
output FLASH_SEL;
output BRK_SEL;
output BRK_PAGE;
output RAM_SEL;
output RAM_PAGE;



reg [5:0] MemMap;
reg D0;
reg FLASH_SEL;
reg BRK_SEL;
reg BRK_PAGE;
reg RAM_SEL;
reg RAM_PAGE;

/*
reg [7:0] Instruc;

assign AD = (A < 'h FE) && PSEN ? Instruc : 8'hz;
always @(AD or A or WR or RESET or PSEN)
begin
if(A == 'h FF && !RESET && !PSEN)
@(posedge WR) Instruc = AD;
else if (RESET) Instruc = 0;
end
*/
always @(AD or A or WR or RESET)
begin
if(A == 'h FF)
begin
if(AD[7:5] == 0 && !RESET)
@(posedge WR) MemMap[5:0] = AD[5:0];
else if (RESET)MemMap[5:0] = 0;

end
end

 

[glen herrmannsfeldt]

Davidg wrote:

If I un-comment the peice of code below, it all compiles. If it is as
below (commented out)in this module, and I place that peice of code in
a different module, the compiler says that Tri-State buffer 'AD' will
be permanently disabled. Any suggestions why this happens? Very
frustating for us nubees

(snip)

AD;

(snip)

/*
reg [7:0] Instruc;

assign AD = (A < 'h FE) && PSEN ? Instruc : 8'hz;

(snip)

If you comment out the only ASSIGNment to AD, there is nothing
to drive it.

It should be a warning, though. It is perfectly legal
to have a permanently disabled tri-state buffer, as it is legal to
have an output permanently high or low.

-- glen

 

[Davidg]

glen herrmannsfeldt <gah@ugcs.caltech.edu> wrote in message news:<cnjanu$qdl$1@gnus01.u.washington.edu>...

Davidg wrote:

If I un-comment the peice of code below, it all compiles. If it is as
below (commented out)in this module, and I place that peice of code in
a different module, the compiler says that Tri-State buffer 'AD' will
be permanently disabled. Any suggestions why this happens? Very
frustating for us nubees

(snip)

inout [7:0] AD;

(snip)

/*
reg [7:0] Instruc;

assign AD = (A < 'h FE) && PSEN ? Instruc : 8'hz;

(snip)

If you comment out the only ASSIGNment to AD, there is nothing
to drive it.

It should be a warning, though. It is perfectly legal
to have a permanently disabled tri-state buffer, as it is legal to
have an output permanently high or low.

-- glen
The code that I commented out in this module was moved to another

module / file. It was not commented out there. I got everything
working in this module and then decided to clean things up. Thats when
the problems started. I want to read from the port in this module and
write to the port in the other module.

David