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  #1 (permalink)  
Old 05-03-2006, 02:29 PM
samtee
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Default ISE8.1 inout, tristate Problem?Please help!

Hi,
I use ISE8.1 (webpack) in Verilog. I try to use inout port. Sample code:
module ....(... inout wire[7:0] data, ...);
reg [7:0] buff;
reg hiZ;

assign data=hiZ ? 8'bzzzz_zzzz:buff;
.....
endmodule

When I use xst to synthesis, and when I look at RTL logic , I cannot
find tristate buffer in the circuit. And when I simulate with ModelSIM
XE 6.0d (eval version), I got xxxx instead of zzzz.

Thank you,
Sam
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  #2 (permalink)  
Old 05-03-2006, 03:14 PM
Benjamin Todd
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Default Re: ISE8.1 inout, tristate Problem?Please help!

You can't have internal tristates, unless you're using old Virtex technology
They'll be replaced by equivalent circuits. (like MUXES) (if I recall
correctly)
Ben
"samtee" <[email protected]> wrote in message
news:[email protected]
> Hi,
> I use ISE8.1 (webpack) in Verilog. I try to use inout port. Sample code:
> module ....(... inout wire[7:0] data, ...);
> reg [7:0] buff;
> reg hiZ;
>
> assign data=hiZ ? 8'bzzzz_zzzz:buff;
> ....
> endmodule
>
> When I use xst to synthesis, and when I look at RTL logic , I cannot find
> tristate buffer in the circuit. And when I simulate with ModelSIM XE 6.0d
> (eval version), I got xxxx instead of zzzz.
>
> Thank you,
> Sam



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  #3 (permalink)  
Old 05-04-2006, 12:43 AM
samtee
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Default Re: ISE8.1 inout, tristate Problem?Please help!

Benjamin Todd wrote:
> You can't have internal tristates, unless you're using old Virtex technology
> They'll be replaced by equivalent circuits. (like MUXES) (if I recall
> correctly)
> Ben
> "samtee" <[email protected]> wrote in message
> news:[email protected]
>
>>Hi,
>>I use ISE8.1 (webpack) in Verilog. I try to use inout port. Sample code:
>>module ....(... inout wire[7:0] data, ...);
>>reg [7:0] buff;
>>reg hiZ;
>>
>>assign data=hiZ ? 8'bzzzz_zzzz:buff;
>>....
>>endmodule
>>
>>When I use xst to synthesis, and when I look at RTL logic , I cannot find
>>tristate buffer in the circuit. And when I simulate with ModelSIM XE 6.0d
>>(eval version), I got xxxx instead of zzzz.
>>
>>Thank you,
>>Sam

>
>
>

Thank you fro your respond.
Then, how can I use inout port to conect to other module?
Sam.
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  #4 (permalink)  
Old 05-04-2006, 03:25 AM
Jeff Brower
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Default Re: ISE8.1 inout, tristate Problem?Please help!

Sam-

This type of coding:

assign data = hiZ ? 8'hzz : (buf1 ? buff_1 : 8'hzz);
assign data = hiZ ? 8'hzz : (buf2 ? buff_2 : 8'hzz);

works Ok, it's just not implemented using actual internal tri-states.
Don't worry, tools handle it for you. ISE 7.1.04 may give warnings
about "the following tristate(s) are NOT replaced by logic..." and I
opened a webcase about that, but the word back is "just ignore".

-Jeff

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  #5 (permalink)  
Old 05-04-2006, 07:25 AM
sam
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Default Re: ISE8.1 inout, tristate Problem?Please help!

Jeff Brower wrote:
> Sam-
>
> This type of coding:
>
> assign data = hiZ ? 8'hzz : (buf1 ? buff_1 : 8'hzz);
> assign data = hiZ ? 8'hzz : (buf2 ? buff_2 : 8'hzz);
>
> works Ok, it's just not implemented using actual internal tri-states.
> Don't worry, tools handle it for you. ISE 7.1.04 may give warnings
> about "the following tristate(s) are NOT replaced by logic..." and I
> opened a webcase about that, but the word back is "just ignore".
>
> -Jeff
>

Thank you,
However, in ISE8.1 ,it also gives warning "Inout dosenot connect".
What should I do?
Sam.
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  #6 (permalink)  
Old 05-04-2006, 10:28 AM
Benjamin Todd
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Posts: n/a
Default Re: ISE8.1 inout, tristate Problem?Please help!

There must be some dodgy code involved if it's taking the i/o out...


"sam" <[email protected]> wrote in message
news:[email protected]
> Jeff Brower wrote:
>> Sam-
>>
>> This type of coding:
>>
>> assign data = hiZ ? 8'hzz : (buf1 ? buff_1 : 8'hzz);
>> assign data = hiZ ? 8'hzz : (buf2 ? buff_2 : 8'hzz);
>>
>> works Ok, it's just not implemented using actual internal tri-states.
>> Don't worry, tools handle it for you. ISE 7.1.04 may give warnings
>> about "the following tristate(s) are NOT replaced by logic..." and I
>> opened a webcase about that, but the word back is "just ignore".
>>
>> -Jeff
>>

> Thank you,
> However, in ISE8.1 ,it also gives warning "Inout dosenot connect".
> What should I do?
> Sam.



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