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* 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
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
* SPDX-License-Identifier: Apache-2.0
* Complete Digital PLL testbench
.lib "/home/tim/projects/efabless/tech/SW/sky130A/" tt
.include "/home/tim/projects/efabless/tech/SW/sky130A/libs.ref/sky130_fd_sc_hd/spice/sky130_fd_sc_hd.spice"
.include "digital_pll.spice"
.option TEMP=27
* .option RELTOL=1.0E-2
* Instantiate the digital PLL
X0 vdd vss reset osc clkp1 clkp0 div4 div3 div2 div1 div0 digital_pll
* Power supply (note that all logic is 1.8V here)
V0 vdd vss PWL(0.0 0.0 25n 1.8)
V1 vss 0 0.0
* Fixed divider value (connect resistors to power or ground)
* divider value = 16 (10MHz * 16 = 160MHz clock)
R0 div4 vdd 1
R1 div3 gnd 1
R2 div2 gnd 1
R3 div1 gnd 1
R4 div0 gnd 1
* Run oscillator at 10MHz
* Because DFFs don't handle reclocking well, keep the edges sharp.
V2 osc vss PULSE(0.0 1.8 5n 10p 10p 50n 100n)
* Reset pulse
V3 reset vss PWL(0.0 1.8 0.1u 1.8 0.101u 0.0)
* Transient analysis. Note that trim updates every four cycles, or about
* three updates per microsecond. To update all 17 trim bits requires
* 6us.
tran 1n 8u
plot V(osc)
plot V(clkp0) V(clkp1)