Description

The PWM In functionality of the OPAL-RT Board driver provides the simulation with the pulse width measurement acquisition data obtained from the digital input channels of the OP5353 modules installed in the simulator.
In the case of the OP4200 chassis, the OP5353 module is incorporated into the I/O cassette with ID OP4250-1.

The driver provides the simulation with each input channel's frequency (measured in Hz) and duty cycle (measured as a fraction of the period) after doing a quick processing of the PWM signals received by the physical modules.
The minimum measurable frequency is 100 Hz.

The duty cycle and carrier frequency are measured using the relation between the rising and falling edges of the input signal. When the input is not switching (for example when the duty cycle is 0 or 1), the PWM In driver cannot establish whether it's the frequency that became slower or the duty cycle that is 0 or 1, until it reaches a supported timeout.
Therefore the equation for the duty cycle is: 

When there is no physical input, the values reported in the model are of around 95 Hz for the frequency and 0 for the duty cycle.

Usage

Once the bitstream configuration file has been parsed, the location of the digital input modules becomes visible to the user. The channels of the modules are grouped into bunches of 8. By clicking on each group of 8, the user has access to the configurable options of the group.

Bitstreams generated with an RT-XSG version of 3.1.2 or later offer the possibility of using the selectable digital input-output feature (SDIO).
The SDIO feature gives the user the option to switch between the type of functionality (either static, PWM or Event Detector) for a group of channels.
The user will know if the bitstream offers the feature as soon as its configuration is loaded in the main section of the current board's configuration page.
Verifying that a bitstream is SDIO-capable is done in the channel group configuration section. If the bitstream has the feature then a drop-down list will be present to choose the functionality. If it does not, the functionality will be displayed as a non-editable field (i.e. grayed out).

Channel group configuration

• Name
  The name of the channel group denotes the physical channels of the digital input module the current configuration will be applied to.
  
  
• Enable
  Checking this box will enable the acquisition of PWM data for the channels in the group once the simulation has started, provided that the type of functionality is set to Pulse width modulated (see item below for more detail).
  Clicking on Enable also makes the connection points for each of the 8 channels' frequency and duty cycle connection points available in HYPERSIM. This means that if the user wishes to display and/or monitor these two characteristics of the digital signals, connections must be made between points in the model and the PWM input connectable points.
  
  
• Digital type
  In case the bitstream is SDIO-capable, this field will take the form of a drop-down list. This list provides the user the choices for the type of functionality to be applied for the current group of 8 digital input channels. To receive PWM inputs, the option Pulse width modulated must be chosen.
  Otherwise, if the bitstream is not SDIO-capable, this field will be seen as non-editable. This means that the 8 channels in the current group can only operate with the functionality described in the grayed-out field. For receiving PWM inputs, please verify that the field displays Pulse width modulated.

Signals configuration

Channels in pulse width measurement groups do not have any parameters to configure.

Characteristics and limitations

For the connector pin assignments, users should refer to the carrier documentation.

The current version of the pulse width measurement input functionality of the OPAL-RT Board driver has the following limitations:

• For a correct functionality, the frequency of the PWM signals has to be between 100 Hz and 190 kHz