Setup and Hold Time Parameters for Testbench

This page describes configuration parameters that reside in the HDL Code Generation > Test Bench tab of the Configuration Parameters dialog box. Using the parameters in this tab, you can specify the setup time for data input and hold time for data input and forced reset signal signals.

Hold time (ns)

Specify a hold time, in nanoseconds, for input signals and forced reset input signals.

Settings

Default: 2 (given the default clock period of 10 ns)

The hold time defines the number of nanoseconds that reset input signals and input data are held past the clock rising edge. The hold time is expressed as a positive integer or double (with a maximum of 6 significant digits after the decimal point).

Tips

The specified hold time must be less than the clock period (specified by the Clock high time and Clock low time properties).
This option applies to reset input signals only if Force reset is selected.

Usage Notes

Hold Time for Reset Input Signals

The hold time is the amount of time that reset input signals and input data are held past the clock rising edge. The following figures show the application of a hold time (t_hold) for reset and data input signals when the signals are forced to active high and active low.

Hold Time for Data Input Signals

Note

A reset signal is always asserted for two cycles plus t_hold.

Dependencies

This option is disabled if you select the entire model. Select the DUT instead for Generate HDL for setting.

Command-Line Information

Property: HoldTime

Type: integer

Value: positive integer

Default: 2

To set this property, use hdlset_param or makehdltb. To view the property value, use hdlget_param.

For example, you can specify this parameter for the symmetric_fir subsystem inside the sfir_fixed model using either of these methods.

Pass the property as an argument to the makehdltb function.

makehdltb('sfir_fixed/symmetric_fir', ... 
            'HoldTime', 4)

When you use hdlset_param, you can set the parameter on the model and then generate HDL code using makehdltb.
```
hdlset_param('sfir_fixed', 'HoldTime', 4)
makehdltb('sfir_fixed/symmetric_fir')
```

Setup time (ns)

Display setup time for data input signals.

Settings

Default: None

This is a display-only field, showing a value computed as (clock period - HoldTime) in nanoseconds.

Dependency

The value displayed in this field depends on the clock rate and the values of the Hold time property.

This option is disabled if you select the entire model. Select the DUT instead for Generate HDL for setting.

Command-Line Information

Because this is a display-only field, a corresponding command-line property does not exist.