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# DRC errors in detailed routing - "Metal spacing violation"
Tool: Detailed Routing
Subcategory: DRC violation
## Conversation
### oharboe
I think this is happening because two macros that need straight vertical wires between them don't have IO pins lined up and then the wires between the macros are criss-crossing.
What is the difference and purpose of `MACRO_PLACE_HALO` vs `MACRO_PLACE_CHANNEL` and where do I use them, in the macro or where I'm using the macro from?
Some thoughts on what I might do:
- I could modify the halo macro to have a big enough "halo" (black area) where the wires can move horizontally to line up better with their destination pin in the other macro.
- I could fix the io pin locations and floorplan so the router is able to use straight vertical wires instead of crisscrossing between two macros. This would reduce the need for a big halo.
### vijayank88
@oharboe
Variable description found here: https://openroad-flow-scripts.readthedocs.io/en/latest/user/FlowVariables.html#floorplan
### maliberty
Note that mpl distinguished halo vs channel but mpl2 just uses halo. The distinction is that a channel is the space between two macros but the halo applies on all sides of the macro.
I can't tell much from the picture.
### maliberty
The setting are for x & y separately. Usually they are the same
### maliberty
Imagine channel=10 and halo=5. Then macros must be 10 apart but standard cells must be 5 away from a macro. It is moot with mpl2.
### oharboe
Updated docs in pull request based on the above: https://github.com/The-OpenROAD-Project/OpenROAD-flow-scripts/pull/1007
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