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Hard macro placement when no pins face each other

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biju4u90

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Suppose I have 2 hard macros and both of them do not have any pins facing each other. In such a scenario, can I keep those 2 macros at close proximity? Or is there any minimum distance criteria even if there are no pins on the face to face sides of the hard macros?
 

you have to respect all the spacing rules of the technology, that is for sure. the problem is that the macros are just abstracts of the hard IP, they have OBS layers for metals and vias typically, but they don't have special purpose layers like SRAM markers.

the best way to find out is to check the documentation of the IP. the provider is usually very straightforward about what you can and can't do. running a full DRC after initial floorplan is done is always a good idea.
 

What is an OBS layer? What is the use of such a special layer? Can you please explain? What is the use of special purpose layers like SRAM markers?
Suppose I don't have any restriction from the IP provider regarding IP placement. In such a scenario, can I place two macros with zero pins on facing sides too close to each other or touching each other?
 

OBS = obstruction. it's not always a physical layer that will be fabbed, sometimes it's only logical. open any LEF file in a text editor and you will see lots of OBS lines.

SRAM markers, as the name hints, mark where in your chip you have SRAMs. The DRC rules for SRAMs are completely different than from the rest of the chip.

Even if no additional restrictions exist, you will always have to respect the foundry rules. if both of your IPs have M1, then you have to space the macros such that the M1 minimum spacing is not violated.
 
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