6 LEF Writer Routines

You can use the Cadence^® Library Exchange Format (LEF) writer routines to create a program that outputs a LEF file. The LEF writer routines correspond to the sections in the LEF file. This chapter describes the routines listed below that you need to write a particular LEF section.


Routines	LEF File Sections
LEF Writer Setup and Control	Initialization and global variables
Bus Bit Characters	BUSBITCHARS statement
Clearance Measure	CLEARANCEMEASURE statement
Divider Character	DIVIDERCHAR statement
Extensions	Extensions statement
Layer (Cut, Masterslice, Overlap, Implant)	LAYER sections about cut, masterslice, overlap, and implant layers
Layer (Routing)	LAYER section about routing layers
Macro	MACRO section
Macro Obstruction	OBS section within a MACRO section
Macro Pin	PIN section within a MACRO section
Macro Pin Port	PORT section within a PIN section
Manufacturing Grid	MANUFACTURINGGRID statement
Maximum Via Stack	MAXVIASTACK statement
Nondefault Rule	NONDEFAULTRULE section
Property	PROPERTY statement in a VIA, VIARULE, LAYER, MACRO or NONDEFAULTRULE section
Property Definitions	PROPERTYDEFINTIONS statement
Same-Net Spacing	SPACING statement
Site	SITE statement
Units	UNITS statement
Use Min Spacing	USEMINSPACING statement
Version	VERSION statement
Via	VIA section
Via Rule	VIARULE statement
Via Rule Generate	VIARULEGENERATE statement

LEF Writer Setup and Control

The LEF writer setup and control routines initialize the reader and set global variables that are used by the reader. You must begin and end a LEF file with the lefwInit and lefwEnd routines. All other routines must be used between these two routines. The remaining routines described in this section are provided as utilities. For examples of the routines described, see "Setup Examples".

All routines return 0 if successful.

lefwInit

Initializes the LEF writer. This routine must be used first.

	MAXXY	Uses the larger x and y distances for spacing between objects.
	EUCLIDEAN	Uses euclidean distance for spacing between objects.

	HORIZONTAL	Routing parallel to the x axis is preferred.
	VERTICAL	Routing parallel to the y axis is preferred.
	DIAG45	Routing along a 45-degree angle is preferred.
	DIAG135	Routing along a 135-degree angle is preferred.

	INSIDECORNER	Applies to consecutive edges of an inside corner that are less than distance.
	OUTSIDECORNER	Applies to consecutive edges of an outside corner that are less than distance.
	STEP	Applies to consecutive edges of a step that are less than distance.

*If Value1* equals:**	*Then Value2 is:*
COVER	Optional and can be BUMP.
BLOCK	Optional and can be BLACKBOX or SOFT.
PAD	Optional and can be INPUT, OUTPUT, INOUT, POWER, SPACER, or AREAIO.
CORE	Optional and can be FEEDTHRU, TIEHIGH, TIELOW, SPACER, ANTENNACELL, or WELLTAP.
ENDCAP	Required and can be PRE, POST, TOPLEFT, TOPRIGHT, BOTTOMLEFT, or BOTTOMRIGHT.

	NULL	Ignores the argument.
	DEFAULT	Identifies the via as the default via.

	X	Defines the site as symmetric about the x axis.
	Y	Defines the site as symmetric about the y axis.
	R90	Defines the site as symmetric when rotated 90 degrees.

	ON	Spacing is computed as if the MACRO OBS shapes were min-width wires. Some LEF models abstract many min-width wires as a single large OBS shape; therefore using wide wire spacing would be too conservative.
	OFF	Spacing is computed to MACRO OBS shapes as if they were actual routing shapes. A wide OBS shape would use wide wire spacing rules, and a thin OBS shapes would use thin wire spacing rules.

LEF 5.8 C/C++ Programming Interface (Open Licensing Program)

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