Create power_control.rst

docs/other/power_control.rst

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+.. raw:: html
+
+   <!---
+   # SPDX-FileCopyrightText: 2020 Efabless Corporation
+   #
+   # Licensed under the Apache License, Version 2.0 (the "License");
+   # you may not use this file except in compliance with the License.
+   # You may obtain a copy of the License at
+   #
+   #      http://www.apache.org/licenses/LICENSE-2.0
+   #
+   # Unless required by applicable law or agreed to in writing, software
+   # distributed under the License is distributed on an "AS IS" BASIS,
+   # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   # See the License for the specific language governing permissions and
+   # limitations under the License.
+   #
+   # SPDX-License-Identifier: Apache-2.0
+   -->
+
+======================
+Caravel Power control
+======================
+
+The user project power control register is a "reserved" register that is
+intended for future use with on-chip LDOs to power the user project
+area.  In the current version of the Caravel chip, it has no function.
+
+In the current version of the Caravel chip, all user area power supplies
+are provided by voltage regulators on the demonstration/development
+board.
+
+**The usable ranges of these power supplies is**:
+
+user1 vccd (VCCD1) = ``1.8V``
+user2 vccd (VCCD2) = ``1.8V``
+
+user1 vdda (VDDA1) = ``1.8V`` to ``5.5V`` (nominally ``3.3V``)
+user2 vdda (VDDA2) = ``1.8V`` to ``5.5V`` (nominally ``3.3V``)
+
+It is the responsibility of the user project area designer to ensure that
+the value of VDDA1 and VDDA2 is compatible with the circuitry connected
+to it in the user project.
+
+--------------------------------------------------------------------------
+
+- Register name = ``reg_mprj_pwr``
+- Memory location = ``0x26000004``
+- Housekeeping SPI location = ``0x6e``
+
++------+-------+-------+-------+-------+-------+-------+-------+-------+
+|      |   7   |   6   |   5   |   4   |   3   |   2   |   1   |   0   |
++------+-------+-------+-------+-------+-------+-------+-------+-------+
+| 0x6e |       |       |       |       | user1 | user2 | user1 | user2 |
+|      |       |       |       |       | vccd  | vccd  | vdda  | vdda  |
++------+-------+-------+-------+-------+-------+-------+-------+-------+
+