mirror of https://github.com/VLSIDA/OpenRAM.git
62 lines
2.7 KiB
Python
62 lines
2.7 KiB
Python
# See LICENSE for licensing information.
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#
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# Copyright (c) 2016-2019 Regents of the University of California and The Board
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# of Regents for the Oklahoma Agricultural and Mechanical College
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# (acting for and on behalf of Oklahoma State University)
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# All rights reserved.
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#
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import debug
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import bitcell_base
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from tech import cell_properties as props
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from tech import parameter
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class replica_bitcell_1rw_1r(bitcell_base.bitcell_base):
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"""
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A single bit cell which is forced to store a 0.
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This module implements the single memory cell used in the design. It
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is a hand-made cell, so the layout and netlist should be available in
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the technology library. """
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pin_names = [props.bitcell.cell_1rw1r.pin.bl0,
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props.bitcell.cell_1rw1r.pin.br0,
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props.bitcell.cell_1rw1r.pin.bl1,
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props.bitcell.cell_1rw1r.pin.br1,
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props.bitcell.cell_1rw1r.pin.wl0,
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props.bitcell.cell_1rw1r.pin.wl1,
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props.bitcell.cell_1rw1r.pin.vdd,
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props.bitcell.cell_1rw1r.pin.gnd]
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type_list = ["OUTPUT", "OUTPUT", "OUTPUT", "OUTPUT", "INPUT", "INPUT", "POWER", "GROUND"]
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def __init__(self, name):
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super().__init__(name)
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debug.info(2, "Create replica bitcell 1rw+1r object")
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def get_stage_effort(self, load):
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parasitic_delay = 1
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size = 0.5 #This accounts for bitline being drained thought the access TX and internal node
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cin = 3 #Assumes always a minimum sizes inverter. Could be specified in the tech.py file.
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read_port_load = 0.5 #min size NMOS gate load
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return logical_effort.logical_effort('bitline', size, cin, load+read_port_load, parasitic_delay, False)
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def input_load(self):
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"""Return the relative capacitance of the access transistor gates"""
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# FIXME: This applies to bitline capacitances as well.
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# FIXME: sizing is not accurate with the handmade cell. Change once cell widths are fixed.
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access_tx_cin = parameter["6T_access_size"]/drc["minwidth_tx"]
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return 2*access_tx_cin
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def build_graph(self, graph, inst_name, port_nets):
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"""Adds edges to graph. Multiport bitcell timing graph is too complex
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to use the add_graph_edges function."""
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pin_dict = {pin:port for pin,port in zip(self.pins, port_nets)}
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pins = props.bitcell.cell_1rw1r.pin
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#Edges hardcoded here. Essentially wl->bl/br for both ports.
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# Port 0 edges
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graph.add_edge(pin_dict[pins.wl0], pin_dict[pins.bl0], self)
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graph.add_edge(pin_dict[pins.wl0], pin_dict[pins.br0], self)
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# Port 1 edges
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graph.add_edge(pin_dict[pins.wl1], pin_dict[pins.bl1], self)
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graph.add_edge(pin_dict[pins.wl1], pin_dict[pins.br1], self)
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