Bi-directional I/O Pads

016_cell : Bi-directional I/O Pads

Minimum Required Versions: AccuCell 2.6.0.R, SmartSpice 4.6.2.R

This example explains the characterization and modeling options for a bi-directional I/O Pad cell using the embedded SmartSpice SPICE engine to perform characterization.

Pin A is an input pin and pin EN is the enable input pin and pin PAD is an input/output pin which are characterized for input capacitance and hidden power. Arcs for each pairing of input to output are characterized separately for difference side-input state conditions to account for all possible effects if this option is selected. Pins Y and PAD are the output pins which are characterized for delay. The PAD input/output pin operates from a different 3.3V supply from the rest of the cell logic and accepts 3.3V input swings.

The following additional .cfg file commands are used when characterizing I/O pad cells:

PAD specifies that a pin is of type PAD.

INOUT specifies the pin is bi-directional

PIN_RAIL2RAIL specifies pins that operate with inputs other than the core supply voltage

SUPPLIES specifies additional power supply voltages other than the global core power.

Additionally, the commands CAP_TABLE, SLOPE_TABLE are normally used to define pin-wise characterization conditions in addition to non-pin-wise definitions which apply to all remaining pins. This permits the PAD pin which typically has significantly different characterization requirements to be defined separate from the rest of the library cells.

For additional details on these commands please refer to the AccuCell Reference and AccuCell User's manuals.