Liberate for library file

Hi, Guangjun,

Thanks again. I really grateful that you spend your precious time help me. Your suggestions have a great influence on me. The synthesis tool is RTL complier. For the imcomplete balloon library, I delete some arcs about from  NRESTORE  to Q,and add function attribution manually. The synthesis can run normally. But I don't know if it will influence the later automatic Place and route. I will debug and analyze the related arcs to see if it's invalid.

Thanks again!

Regard,

Fengye

Hi Fengye,

I tried to debug the failed arc. Spice simulation does not show valid transition or expected signal level for  pin=NRESTORE, related_pin=CK, timing_type=removal_rising, when=(!D * !SAVE), rise_constraint. If the cell is designed correctly, then this is not a valid arc. However, it is designer who can tell. If an auto-generated arc is invalid, you can still use the auto-generation flow, but add define_arc -ignore in the template, eg,

define_cell \
-clock { CK } \
-async { SAVE NRESTORE } \
-input { D } \
-output { Q } \
-pinlist { CK D SAVE NRESTORE Q } \
-delay delay_template_7x7 \
-power power_template_7x7 \
-constraint constraint_template_3x3 \
-mpw mpw_template_3x1 \
balloon_sim_nognd

define_arc \
-type hold \
-when "!D * SAVE" \
-pin NRESTORE \
-related_pin CK \
-vector {RxxRx} \       ;#mtach the order to -pinlist

-ignore \
balloon_sim_nognd

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Is this a retention cell with balloon latch? Please refer to this link for syntax of such cells. You may search for "balloon" to find related information. In particular, there is an example on p.485.

https://media.c3d2.de/mgoblin_media/media_entries/659/Liberty_User_Guides_and_Reference_Manual_Suite_Version_2017.06.pdf

According to Liberate manual, the ff/latch group for retention cells have to be added by user. This can be done with -user_data option in write_library command. I believe you already know by now how to use the user_data flow.

one important note: when you use user_data during write_library, you may want to change setting for cell_use_both_ff_latch_groups, eg setting it to 2.

Looking through your script, there are two incorrect settings for power/ground, which should be,

set_gnd -type pwell VPW 0
set_vdd -type nwell VNW 0.99

Regards,

Guangjun

Hi, Guangjun,

I really appreciate your solutions. Your reply is so detailed. With you suggestion and the documment you provided, I think I can get final solution about the characterization of the retention cell.

Thanks again!

Regard,

Fengye