Integer Division

[Bliss]

I am a complete novice to this language. Although I searched a lot for
division of integers in VHDL I couldn't find much. The previous posts
in this group were helpful but since I don't know much at this stage I
couldn't get them fully. Please guide me and suggest some sites which
can provide algorithms and related text regarding integer division.

Another query - does the / sign work in VHDL?

 

[Dwayne Dilbeck]

"/" works if you have defined a procedure or loaded the appropriate IEEE
library.


As for division
http://courses.cs.vt.edu/~cs1104/BuildingBlocks/divide.030.html

"binary" "division" "algorithm " "RTL" turns up some interesting hits on
google.

Were you planing to divide by a constant, a constant power of 2, or some
variable value?
Each can be optimized and instituted differently.

 

[Duane Clark]

I am a complete novice to this language. Although I searched a lot for
division of integers in VHDL I couldn't find much. The previous posts
in this group were helpful but since I don't know much at this stage I
couldn't get them fully. Please guide me and suggest some sites which
can provide algorithms and related text regarding integer division.

Integer division by its very nature requires a lot of logic to
implement. Therefore, doing an integer division requires that you
balance the factors of:
Required resolution
Required latency time/clocks
Required division time/clocks
Resource utilization

The solution you pick is going to depend on how you balance those factors.

Another query - does the / sign work in VHDL?

In simulation, yes. But generally not in synthesis, because the
synthesis tool does not know how to balance your design requirements.

 

[KJ]

Another query - does the / sign work in VHDL?

In simulation, yes. But generally not in synthesis, because the synthesis
tool does not know how to balance your design requirements.

Synthesis sure does support division (depending on the tool). Try
implementing a<= b / c with Quartus and it will synthesize just fine. You
make not like the performance because it is a hunk-o-logic but when you say
you want "a<= b / c" that combinatorially implements that logic that you
requested.

Kevin Jennings

 

[Duane Clark]

Synthesis sure does support division (depending on the tool). Try
implementing a<= b / c with Quartus and it will synthesize just fine. You
make not like the performance because it is a hunk-o-logic but when you say
you want "a<= b / c" that combinatorially implements that logic that you
requested.

Hmm.. a combinatorial implementation. A somewhat scary thought But
yea, I could see synthesis tools supporting division, especially if it
would support absorbing registers following the division into a pipeline
(something like XST does already with multipliers). That would be a
useful feature.

 

[Philip Herzog]

In simulation, yes. But generally not in synthesis, because the
synthesis tool does not know how to balance your design requirements.

Xilinx ISE 9.2 does synthesize it - if the divisor is a constant and a
power of 2, that is. It is synthesized as a shift then.

- Philip

 

[jeppe]

Check this page: Division

This gives a more interactive presentation of division: Opar1
Jeppe

 

[Bliss]

"/" works if you have defined a procedure or loaded the appropriate IEEE
library.

As for divisionhttp://courses.cs.vt.edu/~cs1104/BuildingBlocks/divide.030.html

"binary" "division" "algorithm " "RTL" turns up some interesting hits on
google.

Were you planing to divide by a constant, a constant power of 2, or some
variable value?
Each can be optimized and instituted differently.

Thanks for replies. The binary division link was of great help.
Actually I don't need a hefty and precise code for the division, just
a simple and approx. one. It's a small part of our big final year
project. So, at the Under grad level a not so accurate code would do.

 

[Dal]

I am a complete novice to this language. Although I searched a lot for
division of integers in VHDL I couldn't find much. The previous posts
in this group were helpful but since I don't know much at this stage I
couldn't get them fully. Please guide me and suggest some sites which
can provide algorithms and related text regarding integer division.

Another query - does the / sign work in VHDL?

Note if by simple you mean your dividend or divisor is constant and/or
your integers have a small range it may be efficient to implement the
divide as a look up table.

 

[Bliss]

Note if by simple you mean your dividend or divisor is constant and/or
your integers have a small range it may be efficient to implement the
divide as a look up table.

No they are variables. By simple I mean that I can compromise on
accuracy and the result needn't be a floating point no.