Mentor v8.6_4 manual Set Zhold Behavior, ∙ OFf

Command Dictionary Set Zhold Behavior

Set Zhold Behavior

Tools Supported: FastScan

Scope: All modes

Usage

SET ZHold Behavior OFf ON

Description

Specifies whether ZHOLD gates retain their state values.

The ZHOLD gate allows FastScan to model tri-state nets so that they can retain the previous state value when the net goes to a high impedance (Z) value. ZHOLD gates normally require clock sequential patterns to utilize this capability. But, if a ZHOLD gate is set to a fixed binary value when the clocks are off, the ZHOLD gate can retain that value for combinational patterns. The combinational fault simulation does not consider the fault effect on the retained value.

By invocation default, FastScan assumes the retained value is always the clock off_state value for both the good machine and the faulty machine simulation.

FastScan cannot assume a state from a previous scan pattern or from a load operation. The amount of time the ZHOLD gate can hold its value is limited to the number of sequential clock cycles.

Arguments

∙OFf

A literal that specifies not to allow ZHOLD gates to retain values.

∙ON

A literal that specifies for FastScan to use ZHOLD gates to retain values subject to restrictions that the rules checker identified. This is the default behavior upon invocation of FastScan.

FastScan and FlexTest Reference Manual, V8.6_4 2-601