import debug import design from tech import drc from pinv import pinv from contact import contact from vector import vector from globals import OPTS class delay_chain(design.design): """ Generate a delay chain with the given number of stages and fanout. This automatically adds an extra inverter with no load on the input. Input is a list contains the electrical effort of each stage. """ def __init__(self, fanout_list, name="delay_chain"): """init function""" design.design.__init__(self, name) # FIXME: input should be logic effort value # and there should be functions to get # area efficient inverter stage list for f in fanout_list: debug.check(f>0,"Must have non-zero fanouts for each stage.") # number of inverters including any fanout loads. self.fanout_list = fanout_list self.num_inverters = 1 + sum(fanout_list) self.num_top_half = round(self.num_inverters / 2.0) c = reload(__import__(OPTS.bitcell)) self.mod_bitcell = getattr(c, OPTS.bitcell) self.bitcell = self.mod_bitcell() self.add_pins() self.create_module() self.route_inverters() self.add_layout_pins() self.DRC_LVS() def add_pins(self): """ Add the pins of the delay chain""" self.add_pin("in") self.add_pin("out") self.add_pin("vdd") self.add_pin("gnd") def create_module(self): """ Add the inverter logical module """ self.inv = pinv(route_output=False) self.add_mod(self.inv) # half chain length is the width of the layout # invs are stacked into 2 levels so input/output are close # extra metal is for the gnd connection U self.height = len(self.fanout_list)*self.inv.height self.width = (max(self.fanout_list)+1) * self.inv.width self.add_inverters() def add_inverters(self): """ Add the inverters and connect them based on the stage list """ self.driver_inst_list = [] self.rightest_load_inst = {} self.load_inst_map = {} for stage_num,fanout_size in zip(range(len(self.fanout_list)),self.fanout_list): if stage_num % 2: inv_mirror = "MX" inv_offset = vector(0, (stage_num+1)* self.inv.height) else: inv_mirror = "R0" inv_offset = vector(0, stage_num * self.inv.height) # Add the inverter cur_driver=self.add_inst(name="dinv{}".format(stage_num), mod=self.inv, offset=inv_offset, mirror=inv_mirror) # keep track of the inverter instances so we can use them to get the pins self.driver_inst_list.append(cur_driver) # Hook up the driver if stage_num+1==len(self.fanout_list): stageout_name = "out" else: stageout_name = "dout_{}".format(stage_num+1) if stage_num == 0: stagein_name = "in" else: stagein_name = "dout_{}".format(stage_num) self.connect_inst([stagein_name, stageout_name, "vdd", "gnd"]) # Now add the dummy loads to the right self.load_inst_map[cur_driver]=[] for i in range(fanout_size): inv_offset += vector(self.inv.width,0) cur_load=self.add_inst(name="dload_{0}_{1}".format(stage_num,i), mod=self.inv, offset=inv_offset, mirror=inv_mirror) # Fanout stage is always driven by driver and output is disconnected disconnect_name = "n_{0}_{1}".format(stage_num,i) self.connect_inst([stageout_name, disconnect_name, "vdd", "gnd"]) # Keep track of all the loads to connect their inputs as a load self.load_inst_map[cur_driver].append(cur_load) else: # Keep track of the last one so we can add the the wire later self.rightest_load_inst[cur_driver]=cur_load def add_route(self, pin1, pin2): """ This guarantees that we route from the top to bottom row correctly. """ pin1_pos = pin1.center() pin2_pos = pin2.center() if pin1_pos.y == pin2_pos.y: self.add_path("metal2", [pin1_pos, pin2_pos]) else: mid_point = vector(pin2_pos.x, 0.5*(pin1_pos.y+pin2_pos.y)) # Written this way to guarantee it goes right first if we are switching rows self.add_path("metal2", [pin1_pos, vector(pin1_pos.x,mid_point.y), mid_point, vector(mid_point.x,pin2_pos.y), pin2_pos]) def route_inverters(self): """ Add metal routing for each of the fanout stages """ for i in range(len(self.driver_inst_list)): inv = self.driver_inst_list[i] for load in self.load_inst_map[inv]: # Drop a via on each A pin a_pin = load.get_pin("A") self.add_via_center(layers=("metal1","via1","metal2"), offset=a_pin.center()) self.add_via_center(layers=("metal2","via2","metal3"), offset=a_pin.center()) # Route an M3 horizontal wire to the furthest z_pin = inv.get_pin("Z") a_pin = inv.get_pin("A") a_max = self.rightest_load_inst[inv].get_pin("A") self.add_via_center(layers=("metal1","via1","metal2"), offset=a_pin.center()) self.add_via_center(layers=("metal1","via1","metal2"), offset=z_pin.center()) self.add_via_center(layers=("metal2","via2","metal3"), offset=z_pin.center()) self.add_path("metal3",[z_pin.center(), a_max.center()]) # Route Z to the A of the next stage if i+1 < len(self.driver_inst_list): z_pin = inv.get_pin("Z") next_inv = self.driver_inst_list[i+1] next_a_pin = next_inv.get_pin("A") y_mid = (z_pin.cy() + next_a_pin.cy())/2 mid1_point = vector(z_pin.cx(), y_mid) mid2_point = vector(next_a_pin.cx(), y_mid) self.add_path("metal2",[z_pin.center(), mid1_point, mid2_point, next_a_pin.center()]) def add_layout_pins(self): """ Add vdd and gnd rails and the input/output. Connect the gnd rails internally on the top end with no input/output to obstruct. """ for driver in self.driver_inst_list: vdd_pin = driver.get_pin("vdd") self.add_layout_pin(text="vdd", layer="metal1", offset=vdd_pin.ll(), width=self.width, height=vdd_pin.height()) gnd_pin = driver.get_pin("gnd") self.add_layout_pin(text="gnd", layer="metal1", offset=gnd_pin.ll(), width=self.width, height=gnd_pin.height()) # input is A pin of first inverter a_pin = self.driver_inst_list[0].get_pin("A") self.add_via_center(layers=("metal1","via1","metal2"), offset=a_pin.center()) self.add_layout_pin(text="in", layer="metal2", offset=a_pin.ll().scale(1,0), height=a_pin.cy()) # output is A pin of last load inverter last_driver_inst = self.driver_inst_list[-1] a_pin = self.rightest_load_inst[last_driver_inst].get_pin("A") self.add_via_center(layers=("metal1","via1","metal2"), offset=a_pin.center()) mid_point = vector(a_pin.cx()+3*self.m2_width,a_pin.cy()) self.add_path("metal2",[a_pin.center(), mid_point, mid_point.scale(1,0)]) self.add_layout_pin_segment_center(text="out", layer="metal2", start=mid_point, end=mid_point.scale(1,0))