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Create clamp_list.rst

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.. raw:: html
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# SPDX-FileCopyrightText: 2020 Efabless Corporation
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=========================
Clamp List
=========================
============================ =========================== =================================
Pad Instance Clamp connections
DRN1 SRC1 DRN2 SRC2 B2B
==========================================================================================
sky130_ef_io__vddio_hvc_pad \mgmt_vddio_hvclamp_pad[0] vddio, vssio
sky130_ef_io__vddio_hvc_pad \mgmt_vddio_hvclamp_pad[1] vddio, vssio
sky130_ef_io__vssio_hvc_pad \mgmt_vssio_hvclamp_pad[0] vddio, vssio
sky130_ef_io__vssio_hvc_pad \mgmt_vssio_hvclamp_pad[1] vddio, vssio
sky130_ef_io__vdda_hvc_pad mgmt_vdda_hvclamp_pad vdda, vssa
sky130_ef_io__vssa_hvc_pad mgmt_vssa_hvclamp_pad vdda, vssa
sky130_ef_io__vdda_hvc_pad user1_vdda_hvclamp_pad vdda1, vssa1
sky130_ef_io__vssa_hvc_pad user1_vssa_hvclamp_pad vdda1, vssa1
sky130_ef_io__vdda_hvc_pad user2_vdda_hvclamp_pad vdda2, vssa2
sky130_ef_io__vssa_hvc_pad user2_vssa_hvclamp_pad vdda2, vssa2
sky130_ef_io__vccd_lvc_pad mgmt_vccd_lvclamp_pad vccd, vssio, vccd, vssd, vssa
sky130_ef_io__vssd_lvc_pad mgmt_vssd_lvclmap_pad vccd, vssio, vccd, vssd, vssa
sky130_ef_io__vccd_lvc_pad user1_vccd_lvclamp_pad vccd1, vssd1, vccd1, vssd, vssio
sky130_ef_io__vssd_lvc_pad user1_vssd_lvclmap_pad vccd1, vssd1, vccd1, vssd, vssio
sky130_ef_io__vccd_lvc_pad user2_vccd_lvclamp_pad vccd2, vssd2, vccd2, vssd, vssio
sky130_ef_io__vssd_lvc_pad user2_vssd_lvclmap_pad vccd2, vssd2, vccd2, vssd, vssio
============================ =========================== =================================
Overlay types used:
===================
1. hvc_pad: vddio -> vssio
2. hvc_pad: vdda -> vssa
3. lvc_pad: vccd -> vssio, vccd -> vssd vssa
4. lvc_pad: vccd -> vssd, vccd -> vssdG vssio
**NOTE:**
Type (4) crosses domains, so that the local VCCD has a diode to the
local VSSD and also to the global VSSD. **BUT:** Although vccd goes all the way
around the chip in the form of vcchib, vssd does not, which makes the SRC2
connection effectively unreachable in this configuration, so better to just
change it to vssd1 and vssd2 for the respective domains.
New overlay types created:
==========================
1. sky130_ef_io__vddio_hvc_clamped_pad: sky130_ef_io__vddio_hvc_pad + overlay (1)
2. sky130_ef_io__vssio_hvc_clamped_pad: sky130_ef_io__vssio_hvc_pad + overlay (1)
3. sky130_ef_io__vdda_hvc_clamped_pad: sky130_ef_io__vdda_hvc_pad + overlay (2)
4. sky130_ef_io__vssa_hvc_clamped_pad: sky130_ef_io__vssa_hvc_pad + overlay (2)
5. sky130_ef_io__vccd_lvc_clamped_pad: sky130_ef_io__vccd_lvc_pad + overlay (3)
6. sky130_ef_io__vssd_lvc_clamped_pad: sky130_ef_io__vssd_lvc_pad + overlay (3)
7. sky130_ef_io__vccd_lvc_clamped2_pad: sky130_ef_io__vccd_lvc_pad + overlay (4)
8. sky130_ef_io__vssd_lvc_clamped2_pad: sky130_ef_io__vssd_lvc_pad + overlay (4)
9. sky130_ef_io__vccd_lvc_clamped3_pad: sky130_ef_io__vccd_lvc_pad + overlay (4)
10. sky130_ef_io__vssd_lvc_clamped3_pad: sky130_ef_io__vssd_lvc_pad + overlay (4)
**NOTE:**
The ``clamped3`` pads correspond to a change in the Caravel design for MPW-2,
in which the vccd/vssd domain has continuous supply rings around the chip
periphery. The pad connection of these two pads does not connect to the padframe
power rings, but connects to a separate set of power rails in the chip core.