OpenRAM/compiler/pgates/pbuf.py

# 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
from vector import vector
import pgate
from sram_factory import factory


class pbuf(pgate.pgate):
    """
    This is a simple buffer used for driving loads.
    """
    def __init__(self, name, size=4, height=None):
        
        debug.info(1, "creating {0} with size of {1}".format(name, size))
        self.add_comment("size: {}".format(size))

        self.stage_effort = 4
        self.size = size
        self.height = height

        # Creates the netlist and layout
        pgate.pgate.__init__(self, name, height)

    def create_netlist(self):
        self.add_pins()
        self.create_modules()
        self.create_insts()

    def create_layout(self):
        self.width = self.inv1.width + self.inv2.width
        self.place_insts()
        self.add_wires()
        self.add_layout_pins()
        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 create_modules(self):
        # Shield the cap, but have at least a stage effort of 4
        input_size = max(1, int(self.size / self.stage_effort))
        self.inv1 = factory.create(module_type="pinv",
                                   size=input_size,
                                   height=self.height)
        self.add_mod(self.inv1)
        
        self.inv2 = factory.create(module_type="pinv",
                                   size=self.size,
                                   height=self.height)
        self.add_mod(self.inv2)

    def create_insts(self):
        self.inv1_inst = self.add_inst(name="buf_inv1",
                                       mod=self.inv1)
        self.connect_inst(["A", "zb_int", "vdd", "gnd"])
        
        self.inv2_inst = self.add_inst(name="buf_inv2",
                                       mod=self.inv2)
        self.connect_inst(["zb_int", "Z", "vdd", "gnd"])

    def place_insts(self):
        # Add INV1 to the right
        self.inv1_inst.place(vector(0, 0))

        # Add INV2 to the right
        self.inv2_inst.place(vector(self.inv1_inst.rx(), 0))
        
    def add_wires(self):
        # inv1 Z to inv2 A
        z1_pin = self.inv1_inst.get_pin("Z")
        a2_pin = self.inv2_inst.get_pin("A")
        mid_point = vector(z1_pin.cx(), a2_pin.cy())
        self.add_path("m1", [z1_pin.center(), mid_point, a2_pin.center()])
        
    def add_layout_pins(self):
        # Continous vdd rail along with label.
        vdd_pin = self.inv1_inst.get_pin("vdd")
        self.add_layout_pin(text="vdd",
                            layer="m1",
                            offset=vdd_pin.ll().scale(0, 1),
                            width=self.width,
                            height=vdd_pin.height())
        
        # Continous gnd rail along with label.
        gnd_pin = self.inv1_inst.get_pin("gnd")
        self.add_layout_pin(text="gnd",
                            layer="m1",
                            offset=gnd_pin.ll().scale(0, 1),
                            width=self.width,
                            height=vdd_pin.height())
            
        z_pin = self.inv2_inst.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.inv1_inst.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_stage_efforts(self, external_cout, inp_is_rise=False):
        """Get the stage efforts of the A -> Z path"""
        stage_effort_list = []
        stage1_cout = self.inv2.get_cin()
        stage1 = self.inv1.get_stage_effort(stage1_cout, inp_is_rise)
        stage_effort_list.append(stage1)
        last_stage_is_rise = stage1.is_rise
        
        stage2 = self.inv2.get_stage_effort(external_cout, last_stage_is_rise)
        stage_effort_list.append(stage2)
        
        return stage_effort_list

    def get_cin(self):
        """Returns the relative capacitance of the input"""
        input_cin = self.inv1.get_cin()
        return input_cin