# See LICENSE for licensing information. # # Copyright (c) 2016-2019 Regents of the University of California and The Board # of Regents for the Oklahoma Agricultural and Mechanical College # (acting for and on behalf of Oklahoma State University) # All rights reserved. # import debug import pgate from vector import vector from sram_factory import factory class pdriver(pgate.pgate): """ This instantiates an even or odd number of inverters sized for driving a load. """ def __init__(self, name, inverting=False, fanout=0, size_list=None, height=None, add_wells=True): debug.info(1, "creating pdriver {}".format(name)) self.stage_effort = 3 self.height = height self.inverting = inverting self.size_list = size_list self.fanout = fanout if not size_list and self.fanout == 0: debug.error("Either fanout or size list must be specified.", -1) if self.size_list and self.fanout != 0: debug.error("Cannot specify both size_list and fanout.", -1) if self.size_list and self.inverting: debug.error("Cannot specify both size_list and inverting.", -1) # Creates the netlist and layout pgate.pgate.__init__(self, name, height, add_wells) def compute_sizes(self): # size_list specified if self.size_list: self.num_stages = len(self.size_list) else: # Find the optimal number of stages for the given effort self.num_stages = max(1, int(round(self.fanout ** (1 / self.stage_effort)))) # Increase the number of stages if we need to fix polarity if self.inverting and (self.num_stages % 2 == 0): self.num_stages += 1 elif not self.inverting and (self.num_stages % 2): self.num_stages += 1 self.size_list = [] # compute sizes backwards from the fanout fanout_prev = self.fanout for x in range(self.num_stages): fanout_prev = max(round(fanout_prev / self.stage_effort), 1) self.size_list.append(fanout_prev) # reverse the sizes to be from input to output self.size_list.reverse() def create_netlist(self): self.compute_sizes() self.add_comment("sizes: {}".format(str(self.size_list))) self.add_pins() self.add_modules() self.create_insts() def create_layout(self): self.place_modules() self.route_wires() self.add_layout_pins() self.width = self.inv_inst_list[-1].rx() self.height = self.inv_inst_list[0].height self.extend_wells() self.route_supply_rails() self.add_boundary() def add_pins(self): self.add_pin("A", "INPUT") self.add_pin("Z", "OUTPUT") self.add_pin("vdd", "POWER") self.add_pin("gnd", "GROUND") def add_modules(self): self.inv_list = [] add_well = self.add_wells for size in self.size_list: temp_inv = factory.create(module_type="pinv", size=size, height=self.height, add_wells=add_well) add_well=False self.inv_list.append(temp_inv) self.add_mod(temp_inv) def create_insts(self): self.inv_inst_list = [] for x in range(1, self.num_stages + 1): # Create first inverter if x == 1: zbx_int = "Zb{}_int".format(x) inst = self.add_inst(name="buf_inv{}".format(x), mod=self.inv_list[x - 1]) self.inv_inst_list.append(inst) if self.num_stages == 1: self.connect_inst(["A", "Z", "vdd", "gnd"]) else: self.connect_inst(["A", zbx_int, "vdd", "gnd"]) # Create last inverter elif x == self.num_stages: zbn_int = "Zb{}_int".format(x - 1) inst = self.add_inst(name="buf_inv{}".format(x), mod=self.inv_list[x - 1]) self.inv_inst_list.append(inst) self.connect_inst([zbn_int, "Z", "vdd", "gnd"]) # Create middle inverters else: zbx_int = "Zb{}_int".format(x - 1) zbn_int = "Zb{}_int".format(x) inst = self.add_inst(name="buf_inv{}".format(x), mod=self.inv_list[x - 1]) self.inv_inst_list.append(inst) self.connect_inst([zbx_int, zbn_int, "vdd", "gnd"]) def place_modules(self): # Add the first inverter at the origin self.inv_inst_list[0].place(vector(0, 0)) # Add inverters to the right of the previous inverter for x in range(1, len(self.inv_inst_list)): loc = vector(self.inv_inst_list[x - 1].rx(), 0) self.inv_inst_list[x].place(loc) def route_wires(self): z_inst_list = [] a_inst_list = [] # inv_current Z to inv_next A for x in range(0, len(self.inv_inst_list) - 1): z_inst_list.append(self.inv_inst_list[x].get_pin("Z")) a_inst_list.append(self.inv_inst_list[x + 1].get_pin("A")) mid_point = vector(z_inst_list[x].cx(), a_inst_list[x].cy()) self.add_path(self.route_layer, [z_inst_list[x].center(), mid_point, a_inst_list[x].center()]) def add_layout_pins(self): z_pin = self.inv_inst_list[len(self.inv_inst_list) - 1].get_pin("Z") self.add_layout_pin_rect_center(text="Z", layer=z_pin.layer, offset=z_pin.center(), width=z_pin.width(), height=z_pin.height()) a_pin = self.inv_inst_list[0].get_pin("A") self.add_layout_pin_rect_center(text="A", layer=a_pin.layer, offset=a_pin.center(), width=a_pin.width(), height=a_pin.height()) def get_sizes(self): """ Return the relative sizes of the buffers """ return self.size_list def get_stage_efforts(self, external_cout, inp_is_rise=False): """ Get the stage efforts of the A -> Z path """ cout_list = [] for prev_inv, inv in zip(self.inv_list, self.inv_list[1:]): cout_list.append(inv.get_cin()) cout_list.append(external_cout) stage_effort_list = [] last_inp_is_rise = inp_is_rise for inv, cout in zip(self.inv_list, cout_list): stage = inv.get_stage_effort(cout, last_inp_is_rise) stage_effort_list.append(stage) last_inp_is_rise = stage.is_rise return stage_effort_list def get_cin(self): """ Returns the relative capacitance of the input """ return self.inv_list[0].get_cin()