# Move `_zero` to special nets

Tool: Detailed Routing

Subcategory: Routing issue

## Conversation

### Blebowski
Hi,
related to previous question, when I proceed to detailed routing, I get:
```
detailed_route -bottom_routing_layer ME2 -top_routing_layer ME5
```
```
[ERROR DRT-0305] Net zero_ of signal type GROUND is not routable by TritonRoute. Move to special nets.
[ERROR GUI-0070] DRT-0305
```

Before, I created my voltage domain and power-grid like so:
```
add_global_connection -net VDD -pin_pattern {^VDD$} -power
add_global_connection -net VSS -pin_pattern {^VSS$} -ground

set_voltage_domain -name VDD_1V2 -power VDD -ground VSS

define_pdn_grid -name "Core"


add_pdn_stripe -layer ME1 -followpins -width 0.2

add_pdn_ring -grid "Core" -layers {ME4 ME5} -widths 4.5 -spacings 1.0 -core_offsets {0 0} -add_connect

add_pdn_stripe -layer ME4 -width 1.5 -pitch 20 -offset 0 -extend_to_core_ring
add_pdn_stripe -layer ME5 -width 1.5 -pitch 20 -offset 0 -extend_to_core_ring

add_pdn_connect -layers {ME1 ME4}
add_pdn_connect -layers {ME1 ME5}

pdngen
```

I thought that "moving zero_ to special nets" can be accomplished by something like:
```
assign_ground_net -domain VDD_1V2 -net [get_nets zero_]
```
But that throws me:
```
[ERROR ODB-0335] group does not exist
[ERROR GUI-0070] ODB-0335
```

Can you help me out here?
Probably I am just doing something super-stupid...


### maliberty
Generally _zero is avoided by using hilomap in yosys.  If you are not using yosys then I suggest using insert_tiecells

### Blebowski
Thanks :)