OpenRAM/compiler/modules/precharge_array.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 design
import debug
from vector import vector
from sram_factory import factory
from globals import OPTS
from tech import layer


class precharge_array(design.design):
    """
    Dynamically generated precharge array of all bitlines.  Cols is number
    of bit line columns, height is the height of the bit-cell array.
    """

    def __init__(self, name, columns, size=1, bitcell_bl="bl", bitcell_br="br", column_offset=0):
        super().__init__(name)
        debug.info(1, "Creating {0}".format(self.name))
        self.add_comment("cols: {0} size: {1} bl: {2} br: {3}".format(columns, size, bitcell_bl, bitcell_br))
        
        self.columns = columns
        self.size = size
        self.bitcell_bl = bitcell_bl
        self.bitcell_br = bitcell_br
        self.column_offset = column_offset

        if OPTS.tech_name == "sky130":
            self.en_bar_layer = "m3"
        else:
            self.en_bar_layer = "m1"
            
        self.create_netlist()
        if not OPTS.netlist_only:
            self.create_layout()

    def get_bl_name(self):
        bl_name = self.pc_cell.get_bl_names()
        return bl_name

    def get_br_name(self):
        br_name = self.pc_cell.get_br_names()
        return br_name

    def add_pins(self):
        """Adds pins for spice file"""
        for i in range(self.columns):
            # These are outputs from the precharge only
            self.add_pin("bl_{0}".format(i), "OUTPUT")
            self.add_pin("br_{0}".format(i), "OUTPUT")
        self.add_pin("en_bar", "INPUT")
        self.add_pin("vdd", "POWER")

    def create_netlist(self):
        self.add_modules()
        self.add_pins()
        self.create_insts()
        
    def create_layout(self):
        self.width = self.columns * self.pc_cell.width
        self.height = self.pc_cell.height

        self.place_insts()
        self.add_layout_pins()
        self.add_boundary()
        self.DRC_LVS()

    def add_modules(self):
        self.pc_cell = factory.create(module_type="precharge",
                                      size=self.size,
                                      bitcell_bl=self.bitcell_bl,
                                      bitcell_br=self.bitcell_br)
        self.add_mod(self.pc_cell)

    def add_layout_pins(self):

        en_pin = self.pc_cell.get_pin("en_bar")
        start_offset = en_pin.lc().scale(0, 1)
        end_offset = start_offset + vector(self.width, 0)
        self.add_layout_pin_segment_center(text="en_bar",
                                           layer=self.en_bar_layer,
                                           start=start_offset,
                                           end=end_offset)

        for inst in self.local_insts:
            self.add_via_stack_center(from_layer=en_pin.layer,
                                      to_layer=self.en_bar_layer,
                                      offset=inst.get_pin("en_bar").center())
            self.copy_layout_pin(inst, "vdd")
            
        for i in range(len(self.local_insts)):
            inst = self.local_insts[i]
            self.copy_layout_pin(inst, "bl", "bl_{0}".format(i))
            self.copy_layout_pin(inst, "br", "br_{0}".format(i))
        
    def create_insts(self):
        """Creates a precharge array by horizontally tiling the precharge cell"""
        self.local_insts = []
        for i in range(self.columns):
            name = "pre_column_{0}".format(i)
            offset = vector(self.pc_cell.width * i, 0)
            inst = self.add_inst(name=name,
                                 mod=self.pc_cell,
                                 offset=offset)
            self.local_insts.append(inst)
            self.connect_inst(["bl_{0}".format(i), "br_{0}".format(i), "en_bar", "vdd"])

    def place_insts(self):
        """ Places precharge array by horizontally tiling the precharge cell"""
        from tech import cell_properties
        xoffset = 0
        for i in range(self.columns):
            tempx = xoffset
            if cell_properties.bitcell.mirror.y and (i + self.column_offset) % 2:
                mirror = "MY"
                tempx = tempx + self.pc_cell.width
            else:
                mirror = ""

            offset = vector(tempx, 0)
            self.local_insts[i].place(offset=offset, mirror=mirror)
            xoffset = xoffset + self.pc_cell.width