Led - L DATABASE EDITOR

OVERVIEW

• Manipulate the L Database by creating and editing schematic and layout cells
• Led inputs:
  • Technology file (ASCII)
  • L files (ASCII and/or binary)
  • GENIE files (ASCII - higher level)
  • Generator programs (L or GENIE)
• Led outputs:
  • Layout/schematic L files (binary or ASCII)
  • Lsim simulator netlist
  • SPICE simulator netlist
  • AutoCells netlist for place and route
• Perform design rule checking from within Led (Lrc tool) of geometric and electrical rules
• Basic procedure:
  1. Create a new schematic or layout cell
  2. Place transistors and/or cells on the page
  3. Add terminals for external I/O signals
  4. Interconnect elements with wires
  5. Write the cell to save it
  6. Write an Lsim netlist for simulation

INVOKING Led FOR STANDARD CELL SCHEMATIC CAPTURE

Led -t scna20orbit -l $MGC_HEP/technology/gdt $MGC_HEP/lib/scna20orbit/gdt/scna20orbit_fast.dir/scna20orbit_I.X [filename]

-t scna20orbit

The Orbit 2.0 micron scalable cmos technology file for MOSIS.
Other available MOSIS-compatible technology files:

• scn12orbit - Orbit 1.2 micron scalable cmos n-well
• scn12hp - H.P. 1.2 micron scalable cmos n-well
• scn08hp - H.P. 0.8 micron scalable cmos n-well
• scn06hp - H.P. 0.6 micron scalable cmos n-well

NOTE: Standard cells are presently available on our system only for the 2.0 micron technology. The other technologies can be used for custom designs.

-l $MGC_HEP/technology/gdt

Path name to the library directory containing the technology files.

$MGC_HEP/lib/scna20orbit/gdt/scna20orbit_fast.dir/scna20orbit_I.X

File containing icons of the standard cells in the Mosis Design Kit.

[filename]

Optional schematic or layout file(s) to load on startup.
(Files may also be loaded during an Led session.)

GENERAL Led USER INTERFACE INFORMATION

LMB (left mouse button)

Use to select objects, points, etc, and to click on menu items.

RMB (right mouse button)

Use to pull up menus in different windows.

Background Menu

- Pop up by pressing RMB in background.
- Use to control window positions, etc.

Led Edit Menu

- Pop up by pressing RMB in an edit window.
- Led Edit Menu options are shown below in the format: Submenu > Option

Hot Keys

-Most menu options can be selected with a single keystroke. -Hot keys are indicated in parentheses below.

STARTING AND FINISHING A SESSION

• Create a new schematic or layout cell:
  • Cells > NEW SCHEMATIC CELL (Hot key: 9)
  • Cells > NEW LAYOUT cell (Hot key: 0)
  • Cells > TOGGLE schem. <-> layout (Hot key: Y)
  
  
• Retrieve an existing schematic or layout cell:
  • Files > READ an L file (Hot key: R)
  
  
• Save a schematic or layout cell or netlist:
  • Files > W. current cell (Hot key: W)
  • Files > W. nets for LSIM (Hot key: h)
  • Files > W. nets for SPICE (Hot key: <)
  • Files > W. ROUTER file (Hot key: N)

ZOOMING & SCANNING THE DISPLAYED PICTURE

• Enlarge (zoom in) to see more detail:
  • Display > Zoom IN (Hot key: 3)
  • Hold down LMB and drag rectangle around area to be enlarged to fit screen
  
  
• Reduce (zoom out) to fit more of schematic/layout on screen:
  • Display > Zoom OUT (Hot key: 5)
  • Hold down LMB and drag rectangle
  
  
• Make entire schematic/layout exactly fit the screen:
  • Display > Zoom to FIT window (Hot key: 6)
  
  
• Move (pan) schematic/layout to place a specified point in the center of the display:
  • Display > CENTER (Hot key: 1)
  • Click LMB on desired center point
  
  
• Plot a grid (useful for placing components):
  • Display > Plot a GRID (Hot key: g)
  
  
• Replot the schematic/layout (to get rid of unwanted object names and grid lines):
  • Display > REPLOT cell (Hot key: TAB)

SELECTING (FINDING) OBJECTS (Cells, terminals, etc.)

• Hold down the LMB and drag a rectangle around the object.
• If more than one object is selected a form will appear listing all objects within the rectangle.
• Click on the desired object name with the LMB.
• An X will appear on the object to indicate that it is selected.

ADDING ELEMENTS TO A SCHEMATIC/LAYOUT

• Add a transistor at the current cursor location (scmos transistor types: TN, TP, TNC)
  • Add > TRANSISTOR (Hot key: v)
  • Click on transistor type in the popup list
  
  
• Add a standard cell to a drawing at the current cursor position. A cell list must have been loaded earlier in the session, or the cells must have been created during the session.
  • Add > INSTANCE of a cell (Hot key: b)
  • Click on the cell type in the popup list
  
  
• Add a power, ground, or signal terminal (external electrical connection) at the cursor location:
  • Add > Add TERMINAL (Hot key: x)
  • Click on a terminal type in the popup list
    • VDD,GND => external power connections
    • OUT,IN,INOUT => external signal connections
  
  
• Elements can often be added more easily by duplicating a cell already in the schematic/layout:
  • Select the element(s)
  • Add > DUPLICATE element (Hot key: d)
  • Move phantom box to desired location and click LMB

DRAWING WIRES TO CONNECT OBJECTS

Basic Procedure:

1. Select an electrical terminal on an object.
   • A terminal name has the form: <objectname>.<termname>
   • Example: pmos0.d (drain of transistor pmos0)
   
   
2. Start a wire at the selected terminal:
   • Add > WIRE (Hot key: a)
   • As the cursor moves, a wire is dynamically drawn from the end point to the cursor position.
   
   
3. Click the LMB to create a "vertex", i.e. to force the wire to bend at the cursor position. A dot is displayed at each created vertex.
   
4. Move the cursor to the destination terminal or wire segment and select it by dragging a box around it. Again, if there is more than one object in the box, select the desired one from the popup list. An X appears at that point and the wire is changed to a dashed line to indicate that it is complete. (The wire changes back to a solid line when the cursor is moved.)

Other Wiring Options

• To terminate a wire at a non-terminal, click to establish an end point, and then pull up the Add Wire menu with the RMB:
  • ADD WIRE control > END wire (Hot key: e)
  
  
• To connect a number of terminals with a single wire:
  • Select the first terminal
  • Add > Add WIRE and continue (Hot key: l)
  • Proceed as in steps 1-4 above, except that as each wire is ended, a new wire is started to be drawn to the next terminal. End the wire via step 5 above.
  
  
• To move a wire from one terminal to another:
  • Select the terminal
  • Alter > Ch. attachment
  • Move to new terminal and select it

DELETING, MOVING, AND ALTERING OBJECTS

• Deleting objects (cells, transistors, terminals, wires):
  • Select the object(s)
  • Alter > Delete element (Hot key: q)
  
  
• Moving object(s):
  • Select the object(s)
  • Alter > Ch. location (move) (Hot key: w)
  • Move phantom box to new location and click
  
  
• Altering an object:
  • Alter > Ch.name (Hot key: n) - change object name
  • Alter > Ch.type (Hot key: y) - change transistor type
  • Alter > Ch.size (Hot key: i) - new transistor W/L values
  • Alter > Ch.rotation (Hot key: .) - rotate 90 degrees
  • Alter > Ch.x reflection (Hot key: ,) - reflect about x axis
  • Alter > Ch.y reflection (Hot key: ,) - reflect about y axis