How to change "Latch Type" in Resource Property Editor

[SYosh17]

Hi all, 

When I looked at the circuit I generated using the latch primitive in the Resource Property Editor, it consisted of LUTs instead of Programmable Registers, which I didn't expect. And the Latch Type was "latch".
However, even though I used the LUT primitive to connect the output of the LUT directly to one of the inputs and configured a latch, the Latch Type was "none".
Could you tell me what the conditions are for the Latch Type to be "latch"?

Since the latch primitive can be specified as the From/To Target of Report Timing, timing information can be obtained. I want to make my own latch with this feature.

I am using Cyclone IV GX and Quartus 18.1.

[sstrell]

A latch by its definition is made of gates, not registers.  Trying to get reliable timing from a latch is not really possible.  Why don't you just use registers?

[SYosh17]

Thank you for your answer.

I'm trying to configure an asynchronous circuit and the circuit doesn't have a global clock in my circuit, so I can't use registers.

[ShengN_Intel]

Hi,

Check this https://www.intel.com/content/www/us/en/docs/programmable/683082/22-2/inferring-latches-correctly.html

Probably can help you.

Note: In some cases, timing analysis does not completely model latch timing. As a best practice, avoid latches unless required by the design and you fully understand the impact.

Best Regards,

Sheng

p/s: If any answer from community or Intel support are helpful, please feel free to mark as solution and give Kudos.

[ShengN_Intel]

Hi

Did you use Continuous Assignment in making your own latch? Continuous Assignment does not infer latch. Check this https://www.intel.com/content/www/us/en/docs/programmable/683082/22-2/inferring-latches-correctly.html

Thanks,

Best regards,

Sheng

[SYosh17]

Thank you very much for your reply.

The document helped me.

I actually tried synthesizing the simple_latch in the document. This circuit was configured using two LUTs, one of which had a "Latch Type" of "latch". The Cyclone IV has 4-input LUTs, so I think this circuit can be configured with a single LUT. Why does this circuit consist of two LUTs? Is there any way to configure this circuit with single LUT?

[ShengN_Intel]

Check this https://www.intel.com/content/www/us/en/programmable/quartushelp/14.1/mergedProjects/hdl/vlog/vlog_pro_latches.htm

This will configure the circuit with single LUT instead of two. Check image below:

Best Regards,

Sheng

p/s: If any answer from community or Intel support are helpful, please feel free to mark as solution and give Kudos.

[ShengN_Intel]

Hi,

Any further update or concern?

Do you need any further help on this?

Thanks,

Best Regards,

Sheng

[ShengN_Intel]

Hi,

Since there are no further feedback for this thread, I shall set this thread to close pending. If you still need further assistance, you are welcome reopen this thread within 20days or open a new thread, some one will be right with you.

Thanks,

Best Regards,

Sheng