WTA VHDL shift left and shift right code different

alpha91 · Apr 1, 2014

Hi, i have learned the shift register code in VHDL as the following:

Code VHDL - [expand]
1
2
3
4
if (reset = '1') then
shift <= '0000" ;
else if (clock' event and (clock= '1')) then
shift <= shift (2 downto 0) & si;

can anyone tell me this is shift left or shift right? because now i need VHDL for both shift left and shift right.

SynthWorks · Apr 1, 2014

alpha91 said:
Hi
shift <= shift (2 downto 0) & si;

This is shift left. Algorithm = remove left most element and add new element on right.

alpha91 · Apr 1, 2014

SynthWorks said:
This is shift left. Algorithm = remove left most element and add new element on right.

thanks for reply. what i need to do if i want to shift right?

axcdd · Apr 1, 2014

Remove right most element and add new element on left ?

shift <= si& shift (3 downto 1);

alpha91 · Apr 1, 2014

axcdd said:
Remove right most element and add new element on left ?

shift <= si& shift (3 downto 1);

i think you are right...

Code VHDL - [expand]
1 2 3 4	if (reset = '1') then shift <= '0000" ; else if (clock' event and (clock= '1')) then shift <= shift (2 downto 0) & si;

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