How to change "Latch Type" in Resource Property Editor

Question

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 · Answer

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?

shengn_altera · Answer

Hi,Check this https://www.intel.com/content/www/us/en/docs/programmable/683082/22-2/inferring-latches-correctly.htmlProbably 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,Shengp/s: If any answer from community or Intel support are helpful, please feel free to mark as solution and give Kudos.

shengn_altera · Answer

HiDid 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.htmlThanks,Best regards,Sheng

shengn_altera · Answer

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.

syosh17 · Answer

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.

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How to change "Latch Type" in Resource Property Editor

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