[LICENSE] Add SPDX headers in ngspice directory

ngspice/digital_pll/digital_pll.spice

@@ -1,4 +1,19 @@
 *---------------------------------------------------------------------------
+* 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
+*
+*     https://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
+*---------------------------------------------------------------------------
 * All-digital Frequency-locked loop
 *---------------------------------------------------------------------------
 * To make this simulatable, the circuit is broken into the ring oscillator

ngspice/digital_pll/digital_pll_controller.xspice

@@ -1,6 +1,7 @@
 * XSpice netlist created from SPICE and liberty sources by spi2xspice.py
-*SPICE netlist created from verilog structural netlist module digital_pll_controller by vlog2Spice (qflow)
+* SPICE netlist created from verilog structural netlist module digital_pll_controller by vlog2Spice (qflow)
 *
+* 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

ngspice/digital_pll/digital_pll_tb.spice

@@ -1,4 +1,19 @@
-*--------------------------------
+*---------------------------------------------------------------------------
+* 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
+*
+*     https://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
+*---------------------------------------------------------------------------
 * Complete Digital PLL testbench
 *--------------------------------
 

ngspice/digital_pll/inverter_tb.spi

@@ -1,3 +1,19 @@
+*---------------------------------------------------------------------------
+* 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
+*
+*     https://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
+*---------------------------------------------------------------------------
 * Simple testbench mainly to check SPICE model conversion from CDL
 * Plots the transient response of the smallest inverter in the HD standard cell library
 

ngspice/digital_pll/ring_osc2x13.spice

@@ -1,4 +1,20 @@
-*SPICE netlist created from verilog structural netlist module ring_osc2x13 by vlog2Spice (qflow)
+*---------------------------------------------------------------------------
+* 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
+*
+*     https://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
+*---------------------------------------------------------------------------
+* SPICE netlist created from verilog structural netlist module ring_osc2x13 by vlog2Spice (qflow)
 * Warning: This file contains <> array delimiters in net names_
 * Note: Library sky130_fd_sc_hd_spice has been removed;  reference library as an
 * include file from the testbench instead_

ngspice/digital_pll/ring_osc2x13.spice.bak

@@ -1,4 +1,20 @@
-*SPICE netlist created from verilog structural netlist module ring_osc2x13 by vlog2Spice (qflow)
+*---------------------------------------------------------------------------
+* 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
+*
+*     https://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
+*---------------------------------------------------------------------------
+* SPICE netlist created from verilog structural netlist module ring_osc2x13 by vlog2Spice (qflow)
 * Warning: This file contains [] array delimiters in net names.
 * Note: Library sky130_fd_sc_hd.spice has been removed;  reference library as an
 * include file from the testbench instead.

ngspice/digital_pll/ring_osc2x13_tb.spice

@@ -1,3 +1,19 @@
+*---------------------------------------------------------------------------
+* 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
+*
+*     https://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
+*---------------------------------------------------------------------------
 * Ring oscillator testbench---simple check of ring oscillator
 * at several trim levels
 

ngspice/digital_pll/ring_osc2x13_tb2.spice

@@ -1,3 +1,19 @@
+*---------------------------------------------------------------------------
+* 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
+*
+*     https://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
+*---------------------------------------------------------------------------
 * Ring oscillator testbench---simple check of ring oscillator
 * at several trim levels
 

ngspice/simple_por/current_test.spice

@@ -1,4 +1,19 @@
-*-------------------------------------------------------------------
+*---------------------------------------------------------------------------
+* 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
+*
+*     https://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
+*---------------------------------------------------------------------------
 * Simple POR circuit for Caravel current mirror test
 *-------------------------------------------------------------------
 

ngspice/simple_por/simple_por.spice

@@ -1,3 +1,19 @@
+*---------------------------------------------------------------------------
+* 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
+*
+*     https://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
+*---------------------------------------------------------------------------
 * NGSPICE file created from simple_por.ext - technology: sky130A
 
 .subckt sky130_fd_pr__cap_mim_m3_2_W5U4AW VSUBS m4_n3179_n3100# c2_n3079_n3000#

ngspice/simple_por/simple_por_tb.spice

@@ -1,4 +1,19 @@
-*-------------------------------------------------------------------
+*---------------------------------------------------------------------------
+* 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
+*
+*     https://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
+*---------------------------------------------------------------------------
 * Simple POR circuit for Caravel
 *-------------------------------------------------------------------
 *

ngspice/simple_por/threshold_test_tb.spice

@@ -1,4 +1,19 @@
-*-------------------------------------------------------------------
+*---------------------------------------------------------------------------
+* 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
+*
+*     https://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
+*---------------------------------------------------------------------------
 * Threshold test for POR circuit
 * Determine gate voltage at which the HV NFET draws 240nA nominal
 *