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Voyager
Voyager
1,074 Views
Registered: ‎06-20-2017

use of std_logic_arith in UG901

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I've noticed some sections of UG901 is correctly the using numeric_std package in the IEEE library but other sections of UG901 are using deprecated packages from Synopsys squatting in the IEEE library, viz.:  std_logic_arith, std_logic_unsigned.

 

For example, the 32-Bit Dynamic Shift Registers Coding Example uses std_logic_unsigned, while the 8-Tap Even Symmetric Systolic FIR filter uses numeric_std.

 

I assume this would simple enough to address in the next release of UG901.

Mike
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Scholar richardhead
Scholar
1,520 Views
Registered: ‎08-01-2012

Re: use of std_logic_arith in UG901

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std_logic_arith/signed/unsiged were never standard in the first place, so cannot become deprecated. They became a defacto standard.

 

Some designers still insist on using them, and Xilinx has historically been like microsoft when it comes to VHDL standards - they'll just do their own thing and just ignore everyone else.

 

So now they have plenty of legacy documentation/code using non-standard VHDL. It doesnt really matter, as the final implementation will still match.

 

I agree, it will not help eradicate their use, but it's here to stay. VHDL 2008 defined standard packages numeric_std_unsigned and numeric_std_signed, which are basically identical to std_logic_unsigned/signed, so standards pedants have already lost.

 

3 Replies
Scholar richardhead
Scholar
1,521 Views
Registered: ‎08-01-2012

Re: use of std_logic_arith in UG901

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std_logic_arith/signed/unsiged were never standard in the first place, so cannot become deprecated. They became a defacto standard.

 

Some designers still insist on using them, and Xilinx has historically been like microsoft when it comes to VHDL standards - they'll just do their own thing and just ignore everyone else.

 

So now they have plenty of legacy documentation/code using non-standard VHDL. It doesnt really matter, as the final implementation will still match.

 

I agree, it will not help eradicate their use, but it's here to stay. VHDL 2008 defined standard packages numeric_std_unsigned and numeric_std_signed, which are basically identical to std_logic_unsigned/signed, so standards pedants have already lost.

 

Voyager
Voyager
1,009 Views
Registered: ‎06-20-2017

Re: use of std_logic_arith in UG901

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@richardhead wrote:

I agree, it will not help eradicate their use, but it's here to stay. VHDL 2008 defined standard packages numeric_std_unsigned and numeric_std_signed, which are basically identical to std_logic_unsigned/signed, so standards pedants have already lost.

 


Ah, thanks.  Learned something...hadn't realized that.

Mike
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Scholar richardhead
Scholar
939 Views
Registered: ‎08-01-2012

Re: use of std_logic_arith in UG901

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I tell a lie, numeric_std_signed doesnt exist. Only numeric_std_unsigned is part of the standard.
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