2.2. Hammer Tech JSON

The tech.json for a given technology sets up some general information about the install of the PDK, sets up DRC rule decks, sets up pointers to PDK files, and supplies technology stackup information. For the full schema of the tech JSON, please see the Full Schema section below, which is derived from the TechJSON Pydantic BaseModel in hammer/tech/__init__.py.

2.2.1. Technology Install

The user may supply the PDK to Hammer as an already extracted directory and/or as a tarball that Hammer can automatically extract. Setting technology.TECH_NAME. install_dir and/or tarball_dir (key is setup in the defaults.yml) will fill in as the path prefix for paths supplied to PDK files in the rest of the tech.json. Below is an example of the installs and tarballs from the ASAP7 plugin.

"name": "ASAP7 Library",
"grid_unit": "0.001",
"installs": [
  {
    "id": "$PDK",
    "path": "technology.asap7.pdk_install_dir"
  },
  {
    "id": "$STDCELLS",
    "path": "technology.asap7.stdcell_install_dir"
  }
],
"tarballs": [
  {
    "root": {
      "id": "ASAP7_PDK_CalibreDeck.tar",
      "path": "technology.asap7.tarball_dir"
    },
    "homepage": "http://asap.asu.edu/asap/",
    "optional": true
  }
],

The id field is used within the file listings further down in the file to prefix path, as shown in detail below. If the file listing begins with cache, then this denotes files that exist in the tech cache, which are generally placed there by the tech plugin’s post-installation script (see ASAP7’s post_install_script method). Finally, the encrypted Calibre decks are provided in a tarball and denoted as optional.

2.2.2. DRC/LVS Deck Setup

As many DRC & LVS decks for as many tools can be specified in the drc decks and lvs decks keys. Additional DRC/LVS commands can be appended to the generated run files by specifying raw text in the additional_drc_text and additional_lvs_text keys. Below is an example of an LVS deck from the ASAP7 plugin.

"lvs_decks": [
  {
    "tool_name": "calibre",
    "deck_name": "all_lvs",
    "path": "ASAP7_PDK_CalibreDeck.tar/calibredecks_r1p7/calibre/ruledirs/lvs/lvsRules_calibre_asap7.rul"
  }
],
"additional_lvs_text": "LVS SPICE EXCLUDE CELL \*SRAM*RW*\"\nLVS BOX \"SRAM*RW*\"\nLVS FILTER \*SRAM*RW*\" OPEN",

The file pointers, in this case, use the tarball prefix because Hammer will be extracting the rule deck directly from the ASAP7 tarball. The additional text is needed to tell Calibre that the dummy SRAM cells need to be filtered from the source netlist and boxed and filtered from the layout.

2.2.3. Library Setup

The libraries key also must be setup in the JSON plugin. This will tell Hammer where to find all of the relevant files for standard cells and other blocks for the VLSI flow. Below is an example of the start of the library setup and one entry from the ASAP7 plugin.

"libraries": [
  {
    "lef_file": "$STDCELLS/techlef_misc/asap7_tech_4x_201209.lef",
    "provides": [
      {
        "lib_type": "technology"
      }
    ]
  },
  {
    "nldm_liberty_file": "$STDCELLS/LIB/NLDM/asap7sc7p5t_SIMPLE_RVT_TT_nldm_201020.lib.gz",
    "verilog_sim": "$STDCELLS/Verilog/asap7sc7p5t_SIMPLE_RVT_TT_201020.v",
    "lef_file": "$STDCELLS/LEF/scaled/asap7sc7p5t_27_R_4x_201211.lef",
    "spice_file": "$STDCELLS/CDL/LVS/asap7sc7p5t_27_R.cdl",
    "gds_file": "$STDCELLS/GDS/asap7sc7p5t_27_R_201211.gds",
    "qrc_techfile": "$STDCELLS/qrc/qrcTechFile_typ03_scaled4xV06",
    "spice_model_file": {
      "path": "$PDK/models/hspice/7nm_TT.pm"
    },
    "corner": {
      "nmos": "typical",
      "pmos": "typical",
      "temperature": "25 C"
    },
    "supplies": {
      "VDD": "0.70 V",
      "GND": "0 V"
    },
    "provides": [
      {
        "lib_type": "stdcell",
        "vt": "RVT"
      }
    ]
  },

The file pointers, in this case, use the $PDK and $STDCELLS prefix as defined in the installs. The corner key tells Hammer what process and temperature corner that these files correspond to. The supplies key tells Hammer what the nominal supply for these cells are. The provides key has several sub-keys that tell Hammer what kind of library this is (examples include stdcell, fiducials, io pad cells, bump, and level shifters) and the threshold voltage flavor of the cells, if applicable. Adding the tech LEF for the technology with the lib_type set as technology is necessary for place and route.

2.2.3.1. Library Filters

Library filters are defined in the LibraryFilter class in hammer/tech/__init__.py. These allow you to filter the entire set of libraries based on specific conditions, such as a file type or corner. Additional functions can be used to extract paths, strings, sort, and post-process the filtered libraries.

For a list of pre-built library filters, refer to the properties in the LibraryFilterHolder class in the same file, accessed as hammer.tech.filters.<filter_method>

2.2.4. Stackup

The stackups sets up the important metal layer information for Hammer to use. Below is an example of one metal layer in the metals list from the ASAP7 example tech plugin.

{"name": "M3", "index": 3, "direction": "vertical", "min_width": 0.072, "pitch": 0.144, "offset": 0.0, "power_strap_widths_and_spacings": [{"width_at_least": 0.0, "min_spacing": 0.072}], "power_strap_width_table": [0.072, 0.36, 0.648, 0.936, 1.224, 1.512]}

All this information is typically taken from the tech LEF and can be automatically filled in with a script. The metal layer name and layer number is specified. direction specifies the preferred routing direction for the layer. min_width and pitch specify the minimum width wire and the track pitch, respectively. power_strap_widths_and_spacings is a list of pairs that specify design rules relating to the widths of wires and minimum required spacing between them. This information is used by Hammer when drawing power straps to make sure it is conforming to some basic design rules.

2.2.5. Sites

The sites field specifies the unit standard cell size of the technology for Hammer.

"sites": [
  {"name": "asap7sc7p5t", "x": 0.216, "y": 1.08}
]

This is an example from the ASAP7 tech plugin in which the name parameter specifies the core site name used in the tech LEF, and the x and y parameters specify the width and height of the unit standard cell size, respectively.

2.2.6. Special Cells

The special_cells field specifies a set of cells in the technology that have special functions. The example below shows a subset of the ASAP7 tech plugin for 2 types of cells: tapcell and stdfiller.

"special_cells": [
  {"cell_type": "tapcell", "name": ["TAPCELL_ASAP7_75t_L"]},
  {"cell_type": "stdfiller", "name": ["FILLER_ASAP7_75t_R", "FILLER_ASAP7_75t_L", "FILLER_ASAP7_75t_SL", "FILLER_ASAP7_75t_SRAM", "FILLERxp5_ASAP7_75t_R", "FILLERxp5_ASAP7_75t_L", "FILLERxp5_ASAP7_75t_SL", "FILLERxp5_ASAP7_75t_SRAM"]},

See the SpecialCell subsection in the Full Schema for a list of special cell types. Depending on the tech/tool, some of these cell types can only have 1 cell in the name list.

There is an optional size list. For each element in its corresponding name list, a size (type: str) can be given. An example of how this is used is for decap cells, where each listed cell has a typical capacitance, which a place and route tool can then use to place decaps to hit a target total decapacitance value. After characterizing the ASAP7 decaps using Voltus, the nominal capacitance is filled into the size list:

{"cell_type": "decap", "name": ["DECAPx1_ASAP7_75t_R", "DECAPx1_ASAP7_75t_L", "DECAPx1_ASAP7_75t_SL", "DECAPx1_ASAP7_75t_SRAM", "DECAPx2_ASAP7_75t_R", "DECAPx2_ASAP7_75t_L", "DECAPx2_ASAP7_75t_SL", "DECAPx2_ASAP7_75t_SRAM", "DECAPx2b_ASAP7_75t_R", "DECAPx2b_ASAP7_75t_L", "DECAPx2b_ASAP7_75t_SL", "DECAPx2b_ASAP7_75t_SRAM", "DECAPx4_ASAP7_75t_R", "DECAPx4_ASAP7_75t_L", "DECAPx4_ASAP7_75t_SL", "DECAPx4_ASAP7_75t_SRAM", "DECAPx6_ASAP7_75t_R", "DECAPx6_ASAP7_75t_L", "DECAPx6_ASAP7_75t_SL", "DECAPx6_ASAP7_75t_SRAM", "DECAPx10_ASAP7_75t_R", "DECAPx10_ASAP7_75t_L", "DECAPx10_ASAP7_75t_SL", "DECAPx10_ASAP7_75t_SRAM"], "size": ["0.39637 fF", "0.402151 fF", "0.406615 fF", "0.377040 fF","0.792751 fF", "0.804301 fF", "0.813231 fF", "0.74080 fF", "0.792761 fF", "0.804309 fF", "0.813238 fF","0.75409 fF", "1.5855 fF", "1.6086 fF", "1.62646 fF", "1.50861 fF", "2.37825 fF", "2.4129 fF", "2.43969 fF", "2.26224 fF", "3.96376 fF", "4.02151 fF", "4.06615 fF", "3.7704 fF"]},

2.2.7. Don’t Use, Physical-Only Cells

The dont_use_list is used to denote cells that should be excluded due to things like bad timing models or layout. The physical_only_cells_list is used to denote cells that contain only physical geometry, which means that they should be excluded from netlisting for simulation and LVS. Examples from the ASAP7 plugin are below:

"dont_use_list": [
    "ICGx*DC*",
    "AND4x1*",
    "SDFLx2*",
    "AO21x1*",
    "XOR2x2*",
    "OAI31xp33*",
    "OAI221xp5*",
    "SDFLx3*",
    "SDFLx1*",
    "AOI211xp5*",
    "OAI322xp33*",
    "OR2x6*",
    "A2O1A1O1Ixp25*",
    "XNOR2x1*",
    "OAI32xp33*",
    "FAx1*",
    "OAI21x1*",
    "OAI31xp67*",
    "OAI33xp33*",
    "AO21x2*",
    "AOI32xp33*"
],
"physical_only_cells_list": [
  "TAPCELL_ASAP7_75t_R", "TAPCELL_ASAP7_75t_L", "TAPCELL_ASAP7_75t_SL", "TAPCELL_ASAP7_75t_SRAM",
  "TAPCELL_WITH_FILLER_ASAP7_75t_R", "TAPCELL_WITH_FILLER_ASAP7_75t_L", "TAPCELL_WITH_FILLER_ASAP7_75t_SL", "TAPCELL_WITH_FILLER_ASAP7_75t_SRAM",
  "FILLER_ASAP7_75t_R", "FILLER_ASAP7_75t_L", "FILLER_ASAP7_75t_SL", "FILLER_ASAP7_75t_SRAM",
  "FILLERxp5_ASAP7_75t_R", "FILLERxp5_ASAP7_75t_L", "FILLERxp5_ASAP7_75t_SL", "FILLERxp5_ASAP7_75t_SRAM"
],

2.2.8. Full Schema

Note that in the the schema tables presented below, items with #/definitions/<class_name> are defined in other schema tables. This is done for documentation clarity, but in your JSON file, those items would be hierarchically nested.

2.2.8.1. TechJSON

type	object
properties
name	Name
	type	string
grid_unit	Grid Unit
	default	null
	anyOf	type	string
		type	null
shrink_factor	Shrink Factor
	default	null
	anyOf	type	string
		type	null
installs	Installs
	default	null
	anyOf	type	array
		items	#/$defs/PathPrefix
		type	null
libraries	Libraries
	default	null
	anyOf	type	array
		items	#/$defs/Library
		type	null
gds_map_file	Gds Map File
	default	null
	anyOf	type	string
		type	null
physical_only_cells_list	Physical Only Cells List
	default	null
	anyOf	type	array
		items	type	string
		type	null
dont_use_list	Dont Use List
	default	null
	anyOf	type	array
		items	type	string
		type	null
drc_decks	Drc Decks
	default	null
	anyOf	type	array
		items	#/$defs/DRCDeck
		type	null
lvs_decks	Lvs Decks
	default	null
	anyOf	type	array
		items	#/$defs/LVSDeck
		type	null
tarballs	Tarballs
	default	null
	anyOf	type	array
		items	#/$defs/Tarball
		type	null
sites	Sites
	default	null
	anyOf	type	array
		items	#/$defs/Site
		type	null
stackups	Stackups
	default	null
	anyOf	type	array
		items	#/$defs/Stackup
		type	null
special_cells	Special Cells
	default	null
	anyOf	type	array
		items	#/$defs/SpecialCell
		type	null
extra_prefixes	Extra Prefixes
	default	null
	anyOf	type	array
		items	#/$defs/PathPrefix
		type	null
additional_lvs_text	Additional Lvs Text
	default	null
	anyOf	type	string
		type	null
additional_drc_text	Additional Drc Text
	default	null
	anyOf	type	string
		type	null

2.2.8.1.1. CellType

type	string
enum	tiehicell, tielocell, tiehilocell, endcap, iofiller, stdfiller, decap, tapcell, driver, ctsbuffer, ctsinverter, ctsgate, ctslogic

2.2.8.1.2. Corner

type	object
properties
nmos	Nmos
	type	string
pmos	Pmos
	type	string
temperature	Temperature
	type	string

2.2.8.1.3. DRCDeck

type	object
properties
tool_name	Tool Name
	type	string
deck_name	Deck Name
	type	string
path	Path
	type	string

2.2.8.1.4. LVSDeck

type	object
properties
tool_name	Tool Name
	type	string
deck_name	Deck Name
	type	string
path	Path
	type	string

2.2.8.1.5. Library

type	object
properties
name	Name
	default	null
	anyOf	type	string
		type	null
ccs_liberty_file	Ccs Liberty File
	default	null
	anyOf	type	string
		type	null
ccs_library_file	Ccs Library File
	default	null
	anyOf	type	string
		type	null
ecsm_liberty_file	Ecsm Liberty File
	default	null
	anyOf	type	string
		type	null
ecsm_library_file	Ecsm Library File
	default	null
	anyOf	type	string
		type	null
corner	default	null
	anyOf	#/$defs/Corner
		type	null
itf_files	default	null
	anyOf	#/$defs/MinMaxCap
		type	null
lef_file	Lef File
	default	null
	anyOf	type	string
		type	null
klayout_techfile	Klayout Techfile
	default	null
	anyOf	type	string
		type	null
spice_file	Spice File
	default	null
	anyOf	type	string
		type	null
gds_file	Gds File
	default	null
	anyOf	type	string
		type	null
milkyway_lib_in_dir	Milkyway Lib In Dir
	default	null
	anyOf	type	string
		type	null
milkyway_techfile	Milkyway Techfile
	default	null
	anyOf	type	string
		type	null
nldm_liberty_file	Nldm Liberty File
	default	null
	anyOf	type	string
		type	null
nldm_library_file	Nldm Library File
	default	null
	anyOf	type	string
		type	null
openaccess_techfile	Openaccess Techfile
	default	null
	anyOf	type	string
		type	null
provides	Provides
	default	null
	anyOf	type	array
		items	#/$defs/Provide
		type	null
qrc_techfile	Qrc Techfile
	default	null
	anyOf	type	string
		type	null
supplies	default	null
	anyOf	#/$defs/Supplies
		type	null
tluplus_files	default	null
	anyOf	#/$defs/MinMaxCap
		type	null
tluplus_map_file	Tluplus Map File
	default	null
	anyOf	type	string
		type	null
verilog_sim	Verilog Sim
	default	null
	anyOf	type	string
		type	null
verilog_synth	Verilog Synth
	default	null
	anyOf	type	string
		type	null
spice_model_file	default	null
	anyOf	#/$defs/SpiceModelFile
		type	null
power_grid_library	Power Grid Library
	default	null
	anyOf	type	string
		type	null
extra_prefixes	Extra Prefixes
	default	null
	anyOf	type	array
		items	#/$defs/PathPrefix
		type	null
def_file	Def File
	default	null
	anyOf	type	string
		type	null

2.2.8.1.6. Metal

A metal layer and some basic info about it. name: Metal layer name (e.g. M1, M2). index: The order in the stackup (lower is closer to the substrate). direction: The preferred routing direction of this metal layer, or RoutingDirection.Redistribution for non-routing top-level redistribution metals like Aluminium. min_width: The minimum wire width for this layer. max_width: The maximum wire width for this layer. pitch: The minimum cross-mask pitch for this layer (NOT same-mask pitch for multiple-patterned layers). Width of routing grid for a given layer. To route denser wires on chip, multiple masks are required. During fabrication, the masks are applied separately with some spatial offsets to achieve denser line patterning. For more information on multiple-patterning, check https://en.wikipedia.org/wiki/Multiple_patterning offset: The routing track offset from the origin for the first track in this layer. (0 = first track is on an axis). power_strap_widths_and_spacings: A list of WidthSpacingTuples that specify the minimum spacing rules for an infinitely long wire of variying width. power_strap_width_table: A list of allowed metal widths in the technology. Widths smaller than the last number must be quantized to a value in the table. grid_unit: The fixed-point decimal value of a minimum grid unit (e.g. 1nm = 0.001). For most technologies, this comes from the technology plugin and is the same for all layers.
type	object
properties
name	Name
	type	string
index	Index
	type	integer
direction	#/$defs/RoutingDirection
min_width	Min Width
	anyOf	type	number
		type	string
max_width	Max Width
	default	null
	anyOf	type	number
		type	string
		type	null
pitch	Pitch
	anyOf	type	number
		type	string
offset	Offset
	anyOf	type	number
		type	string
power_strap_widths_and_spacings	Power Strap Widths And Spacings
	type	array
	items	#/$defs/WidthSpacingTuple
power_strap_width_table	Power Strap Width Table
	type	array
	default
	items	anyOf	type	number
			type	string
grid_unit	Grid Unit
	anyOf	type	number
		type	string

2.2.8.1.7. MinMaxCap

type	object
properties
max_cap	Max Cap
	type	string
min_cap	Min Cap
	type	string

2.2.8.1.8. PathPrefix

A path prefix which defines an identifier and its corresponding path. Example: A PathPrefix(id = “Alib”, path = “/scratch/projectA/mylib”) maps the identifier ‘Alib’ to the path ‘/scratch/projectA/mylib’
type	object
properties
id	Id
	type	string
path	Path
	type	string

2.2.8.1.9. Provide

type	object
properties
lib_type	Lib Type
	type	string
vt	Vt
	default	null
	anyOf	type	string
		type	null

2.2.8.1.10. RoutingDirection

Represents a preferred routing direction for a metal layer. Note that this represents a preferred direction, not a DRC rule.
type	string
enum	vertical, horizontal, redistribution

2.2.8.1.11. Site

A standard cell site, which is the minimum unit of x and y dimensions a standard cell can have. name: The name of this site (often something like “core”) as defined in the tech and standard cell LEFs x: The x dimension y: The y dimension
type	object
properties
name	Name
	type	string
x	X
	anyOf	type	number
		type	string
y	Y
	anyOf	type	number
		type	string

2.2.8.1.12. SpecialCell

type	object
properties
cell_type	#/$defs/CellType
name	Name
	type	array
	items	type	string
size	Size
	default	null
	anyOf	type	array
		items	type	string
		type	null
input_ports	Input Ports
	default	null
	anyOf	type	array
		items	type	string
		type	null
output_ports	Output Ports
	default	null
	anyOf	type	array
		items	type	string
		type	null

2.2.8.1.13. SpiceModelFile

type	object
properties
path	Path
	type	string
lib_corner	Lib Corner
	default	null
	anyOf	type	string
		type	null

2.2.8.1.14. Stackup

A stackup is a list of metals with a meaningful keyword name (for now). TODO: add vias, etc when we need them
type	object
properties
grid_unit	Grid Unit
	anyOf	type	number
		type	string
name	Name
	type	string
metals	Metals
	type	array
	items	#/$defs/Metal

2.2.8.1.15. Supplies

type	object
properties
GND	Gnd
	type	string
VDD	Vdd
	type	string

2.2.8.1.16. Tarball

type	object
properties
root	#/$defs/PathPrefix
homepage	Homepage
	type	string
optional	Optional
	type	boolean
	default	False

2.2.8.1.17. WidthSpacingTuple

A tuple of wire width limit and spacing for generating a piecewise linear rule for spacing based on wire width. width_at_least: Any wires larger than this must obey the minSpacing rule. min_spacing: The minimum spacing for this bin. If a wire is wider than multiple entries, the worst-case (larger) minSpacing wins.
type	object
properties
width_at_least	Width At Least
	anyOf	type	number
		type	string
min_spacing	Min Spacing
	anyOf	type	number
		type	string