Command Dictionary Set Zhold Behavior
FastScan and FlexTest Reference Manual, V8.6_4 2-601
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.