shift_r

[krby_xtrm]

how to include in a package a shift left/right operation??
ex. shift_r(input_vector) or shift_left(input_vector)??

 

[Andy Peters]

krby_xtrm wrote:

how to include in a package a shift left/right operation??
ex. shift_r(input_vector) or shift_left(input_vector)??

VHDL already has a shift operator ...

-a

 

[Mike Treseler]

krby_xtrm wrote:

how to include in a package a shift left/right operation??

The shift operators SLL, SRL, ROL and ROR
are a bit of a mess.

The operators work for
for numeric_std.unsigned and signed
like this:

byte_uns_v := byte_uns_v SLL 1;

The function numeric_std.shift_left(arg,n) is a
function that does the same thing.

byte_uns_v := shift_left(byte_uns_v, 1);

The operators work the same way on the
rarely used bit_vector type, but the
function above does not.

There are no standard or ieee
shift operators for std_logic_vector
but you can use an '&' like this:

byte_std_v := byte_std_v(6 downto 1) & in_v; --shift left

....a style I sometimes think is easier to read in any case

-- Mike Treseler


--PS: Don't ask about SLA. It only works on bit_vector
Use resize for unsigned. Oh my. . .

 

[krby_xtrm]

i know the solution now:
i'll just include this in the package...

-- shift_left --
sdata <= sdata(data'HIGH-1 downto 1) & inp; -- where inp is an input
bit to the shift register
-- same goes with shift_right --
sdata <= inp & sdata(data'HIGH-1 downto 1);

regards,
kerby

Mike Treseler wrote:

krby_xtrm wrote:
how to include in a package a shift left/right operation??

The shift operators SLL, SRL, ROL and ROR
are a bit of a mess.

The operators work for
for numeric_std.unsigned and signed
like this:

byte_uns_v := byte_uns_v SLL 1;

The function numeric_std.shift_left(arg,n) is a
function that does the same thing.

byte_uns_v := shift_left(byte_uns_v, 1);

The operators work the same way on the
rarely used bit_vector type, but the
function above does not.

There are no standard or ieee
shift operators for std_logic_vector
but you can use an '&' like this:

byte_std_v := byte_std_v(6 downto 1) & in_v; --shift left

...a style I sometimes think is easier to read in any case

-- Mike Treseler


--PS: Don't ask about SLA. It only works on bit_vector
Use resize for unsigned. Oh my. . .

 

[jens]

-- shift_left --
sdata <= sdata(data'HIGH-1 downto 1) & inp; -- where inp is an input
bit to the shift register
-- same goes with shift_right --
sdata <= inp & sdata(data'HIGH-1 downto 1);

It seems like this might work a little better:

sdata <= sdata(sdata'HIGH-1 downto 0) & inp; --left
sdata <= inp & sdata(sdata'HIGH downto 1); --right

 

[krby_xtrm]

oh, right... should've been that way. Thanks~!

-krby