Questions about placing pins manually

[b224hisl]

Hi, I'm trying to place pins manually after the floorplan stage, because I don't want to place pins automatically around the die boundary.
I notice that there are some commands related to that. But I'm quite confused about these commands.

1. What's the difference between define_pin_shape_pattern and set_io_pin_constraint
2. There are two commands called place_pins and place_pin, one for placing all pins and the other one is used to place a specific pin. But the later one just has one option -layer, the former one has -hor_layers and -ver_layers. I'm curious why placing pins needs to define hor/ver layers? In my understanding, when placing a pin we just need to define which metal layer the pin is on.
3. For placing pins manually, what's the right order of executing these commands?

Looking forward to your reply, thank you very very much!

[rovinski]

1. define_pin_shape_pattern creates a regular grid where pins can be placed throughout an area. This is mostly used if you want to create pins on your top layer, such as for a block which uses M1-M4 so that pins can be connected on M4 from above. The much more common use case is for advanced packaging. From the README: The define_pin_shape_pattern command can be used to place pins in any metal layer with the minimum allowed spacing to facilitate 3DIC integration of chips using face-to-face packaging technologies. These technologies include micro bumps and hybrid bonding for high density face-to-face interconnect.
   set_io_pin_constraint assumes the normal pin placement rules, where pins will be created only on the die edges and on the routing tracks. The purpose of the command is to restrict where the pin placer will place your pins, such as to specific metal layers or to specific sides of the die. This command is used more often with blocks.
2. place_pins is intended to use the pin placement engine to automatically place pins in valid locations (as determined by the metal layers, routing tracks, and constraints set with set_io_pin_constraint).
   place_pin is a manual command intended to place a pin at an exact location without using the pin placement engine. place_pin has a -layer option because there is only one pin placed so there is only one layer that can be used. place_pins places multiple pins so they can be spread across different layers. -hor_layers and -ver_layers constrain the horizontal layers and vertical layers to use, which is important because these pins are being placed automatically, not manually like with place_pin. In theory the tool could infer the proper direction based on the layer, so I'm not sure why it has to be explicit. It might be to allow forcing of wrong way pins. @eder-matheus do you know?
3. For placing pins manually, you should simply use a long list of place_pin commands for each individual pin (no other commands). An easy way to do this could be to automatically place the pins and then use write_pin_placement to create an executable Tcl file which will individually place each pin. Alternatively if you are looking to create a very specific pin placement, you could generate a pin placement script using a generator script of some kind.

[b224hisl]

Ok, thank you very much, I think that problem has been solved, but another problem arrives. As you can see in this image, my die has its size of 250x130, then I
define_pin_shape_pattern -layer met5 -x_step 2 -y_step 2 -region {64 20 185 116} -size {1 1} and
define_pin_shape_pattern -layer met4 -x_step 2 -y_step 2 -region {64 20 185 116} -size {1 1} ,
then I place pins by place_pins -hor_layers met5 -ver_layers met4. But the pins are still on the boundary:

I would like to place pins like

or

Are there any ways to achieve them?

[eder-matheus]

We do not support two patterns created with the define_pin_shape_pattern command. Only one of them will be used, probably the last one/

To have your pins placed in the grid you created, you have to constrain them to this grid with this command:
set_io_pin_constraint -pin_names * -region "up:*".

Unfortunately, our documentation on this functionality is not clear enough. I will update it to clarify how to use the grid created in the top layer.

[b224hisl]

I also execute set_io_pin_constraint -pin_names * -region "up:*" but it seems to get the same result, the pins are still on the boundary

[eder-matheus]

Do you have a test case you can share? Also, did you remove one of the calls for define_pin_shape_pattern?

[eder-matheus]

Here's one of our unit tests that performs exactly what you're trying to do: https://github.com/The-OpenROAD-Project/OpenROAD/blob/master/src/ppl/test/top_layer7.tcl

[b224hisl]

OK fine, that really helps! Thank you a lot!
Now I have a better understanding of pin placement. You can close this issue now!
But maybe I will update my latter issue related to that topic. Thanks!

[b224hisl]

However, after placing pins manually:

I found that there seems no routes to pins which are placed within the die, is there any way to route to these pins?

@eder-matheus