Modulus 12

[Andrés]

Hi VHDL people,

is it possible to implement a MOD 12 operation
in Hardware ?

The Lattice Synthesizer is not able to use any direct implementation.

Suggestions are welcome.

Best regards

Andrés

 

[Allan Herriman]

On Mon, 14 Feb 2005 13:02:18 +0100, Andrés <nospam_nussspucke@gmx.de>
wrote:

Hi VHDL people,

is it possible to implement a MOD 12 operation
in Hardware ?

The Lattice Synthesizer is not able to use any direct implementation.

Suggestions are welcome.

12 = 4 * 3.

Mod 2**N is trivially easy, and mod 2**N-1 is reasonably easy, once
you understand the maths.

This thread describes how to do a mod 3 operation on a 10 bit number
in 1 CLB:
http://groups-beta.google.com/group/comp.arch.fpga/browse_frm/thread/40b7d07440650599/93bef6826d0a16b3

Regards,
Allan

 

[Andrés]

Andrés wrote:

Hi VHDL people,

is it possible to implement a MOD 12 operation
in Hardware ?

The Lattice Synthesizer is not able to use any direct implementation.

Suggestions are welcome.

Best regards

Andrés

Something additional:

I am using a counter that counts up.

Every time the counter value mod 12 gets zero I want
to make a signal 'l_show_burst_complete' HIGH.

I am implementing a back-to-back write for an DDR SDRAM controller.

Rgds
Andrés

 

[Allan Herriman]

On Mon, 14 Feb 2005 13:30:54 +0100, Andrés <nospam_nussspucke@gmx.de>
wrote:

Andrés wrote:
Hi VHDL people,

is it possible to implement a MOD 12 operation
in Hardware ?

The Lattice Synthesizer is not able to use any direct implementation.

Suggestions are welcome.

Best regards

Andrés

Something additional:

I am using a counter that counts up.

Every time the counter value mod 12 gets zero I want
to make a signal 'l_show_burst_complete' HIGH.

I am implementing a back-to-back write for an DDR SDRAM controller.

That's rather different. You should just make a divide by 12 counter,
and reset it at the same time you reset your main counter.

Regards,
Allan

 

[Tuukka Toivonen]

On 2005-02-14, Allan Herriman <allan.herriman.hates.spam@ctam.com.au.invalid> wrote:

On Mon, 14 Feb 2005 13:02:18 +0100, Andrés <nospam_nussspucke@gmx.de
wrote:

Hi VHDL people,

is it possible to implement a MOD 12 operation
in Hardware ?

The Lattice Synthesizer is not able to use any direct implementation.

Suggestions are welcome.

12 = 4 * 3.

Mod 2**N is trivially easy, and mod 2**N-1 is reasonably easy, once
you understand the maths.

And, to get mod 12 from mod 4 and 3, you use typically "chinese remainder theorem"
or "mixed radix conversion". However, they require multiplications but if you're
lucky those can be done with a few bit shifts. Something to type into Google...