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Old 08-23-2004, 07:29 PM
Brad Smallridge
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Default Xilinx - Proper VHDL for Bidirectional Pins

What is the proper VHDL code for bidirectional pins on a Xilinx chip?
I used the code below but the chip runs hot.


SRAM_BIDIRECTIONAL_PINSrocess(SRAM_W_SIGNAL_5,SR AM_DQA_SIGNAL_5,SRAM_DQB_SIGNAL_5 )
begin
if(SRAM_W_SIGNAL_5 = '1') then
SRAMDQA <= SRAM_DQA_SIGNAL_5;
SRAMDQB <= SRAM_DQB_SIGNAL_5;
else
SRAMDQA <= (others => 'Z');
SRAMDQB <= (others => 'Z');
end if;
end process;

Thanks,

Brad

b r a d @ a i v i s i o n . c o m
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  #2 (permalink)  
Old 08-24-2004, 02:29 AM
Inquiring Guy
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Default Re: Xilinx - Proper VHDL for Bidirectional Pins

You should use tri-state buffers.

SRAMDQA <= SRAM DQA SIGNAL 5 when (SRAM W SIGNAL 5 = '1') else (others => 'Z');

x <= SRAMDQA;
and so on.

x -------------------------|
|
|\ |
SRAMDQASIGNAL5 -------| \__|_______________ SRAMDQA
| /
|/|
|
SRAMWSIGNAL5 -----------|

"Brad Smallridge" <[email protected]> wrote in message news:<[email protected]>...
> What is the proper VHDL code for bidirectional pins on a Xilinx chip?
> I used the code below but the chip runs hot.
>
>
> SRAM BIDIRECTIONAL PINSrocess(SRAM W SIGNAL 5,SRAM DQA SIGNAL 5,SRAM DQ
> B SIGNAL 5 )
> begin
> if(SRAM W SIGNAL 5 = '1') then
> SRAMDQA <= SRAM DQA SIGNAL 5;
> SRAMDQB <= SRAM DQB SIGNAL 5;
> else
> SRAMDQA <= (others => 'Z');
> SRAMDQB <= (others => 'Z');
> end if;
> end process;
>
> Thanks,
>
> Brad
>
> b r a d @ a i v i s i o n . c o m
> --

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