Stimulus Editor

A Stimulus is a sequence of states (= Bits) taken by an I/O pin (see I/O Device Modeling). Three different states are possible:

• 0: low voltage state (0 Bit)

• 1: high voltage state (1 Bit)

• z: idle state

The Stimulus definitions are stored inside Navigation Tree: Technology Stimuli as shown in the figure below:

A Stimulus does not present a complete analog excitation curve. It neither tells about the absolute voltage amplitude nor the transition time during the state changes happen. These important data are supplied by the Signal Models of an I/O Device (see Signal Modeling).

Edit Stimuli

The Stimulus Editor is divided in an upper and a lower part. In the upper part the Name of the specific stimulus can be defined. In addition, the general Stimulus type can be specified and how the Stimulus shall be described regarding Period Time or Duty Cycle. The lower part provides the data table including the defined Stimuli. The columns of the table change according to the settings in the upper part.

Name: Every Stimulus needs a unique name.

Time schedule types

There are three possibilities how the  time schedule for a Stimulus can be defined. A general rule for all possibilities is that two subsequent states build an unit cycle which duration is defined either by Period Time or Frequency.

Pulse Width & Period Time:  

Period Time is the time frame during two sequent states (Bits) have to be executed. Pulse Width defines the time of the high voltage state (1 Bit). Delay enables the user to shift the complete bit sequence by a certain time.

Duty Cycle & Period Time:

Period Time is the time frame during two sequent states (Bits) have to be executed. Duty Cycle defines the time of the high voltage state (1 Bit) as a fraction of the Period Time. Delay enables the user to shift the complete bit sequence by a certain time.

Duty Cycle & Frequency:

Frequency is the inverse of the Period Time and defines the time frame during two sequent states (Bits) have to be executed. Duty Cycle defines the time of the high voltage state (1 Bit) as a fraction of the inverse of Frequency (=Period Time). Delay enables the user to shift the complete bit sequence by a certain time.

Stimulus type: There are four possible types of Stimuli:

• clk-cont: provides a continuous sequence of alternating bits 0 1 0 1 0 1 ...

• sequence: allows a free definition of a bit sequence. The state z turns the active output pin to an receiving input pin. The dialog accepts the definition of a z-state within a not completed unit cycle (e.g.: 01 1z zz z0 10 ...). But it is recommended to complete an active unit cycle before defining one ore more pairs of z-states (e.g.: 01 11 zz zz 10 ...)

• random: provides a random bit sequence. The Weighting field controls the average number of 0 and 1 Bits. A weighting of 50% means the sequence will include an equal average of 0 and 1 Bits. A weighting of 100% means the sequence will include only 1 Bits and a weighting of 0% means there will be only 0 Bits.

• pseudo random bit sequence: provides a standardised bit sequence typically used for signal integrity analysis. The number of pulses can be given in the N (N2 bits). The first N pulses are always 1 Bits.

Stimulus list frame

The frame includes the list of all defined Stimuli. The column types change according to the Time schedule type settings (see Time schedule types).  On the right hand side of the frame there a several buttons enabling the following actions:

• Create new stimulus

• Duplicate stimulus

• Import stimulus from a Stimulus Library file

• Export stimulus to a Stimulus Library file

• Delete all unused stimuli: delete all stimuli which are not used by any I/O device.

• Delete selected stimuli

Four stimuli are predefined:

• Clock: a stimulus of type clk-cont  (see Stimulus type above)

• DDR_Read: a typical bit sequence for reading

• DDR_Write: a typical bit sequence for writing

• Quiet: a sequence of passive states

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