SIS function blocks > SIS I/O Blocks > Logic Solver Discrete Input function block

Logic Solver Discrete Input function block execution

The LSDI function block accesses a single discrete input from a two-state field device and makes the processed physical input available to other function blocks. You can configure inversion on the input value.

The LSDI function block supports block signal status propagation and simulation.

After calculation, the process variable (PV_D) is copied to the output (OUT_D).

I/O Selection

When you configure the Discrete Input function block, you select the input associated with the discrete measurement by configuring the Device Signal Tag (DST) of the IO_IN parameter. You select the DST and the parameter the Discrete Input block accesses. In SLS 1508 systems the input specified can be one of the 16 channels on this logic solver or an input channel on a logic solver on the same controller. In CHARMs Smart Logic Solver systems the input specified can be any of the LS CHARMs of any CSLS in the Local Safety Network.

The only selectable parameter for IO_IN is FIELD_VAL_D — the last discrete value with status reported.

Simulation

To test a module's logic, download to a simulated logic solver (a logic solver assigned to the ProfessionalPLUS workstation), enable the SIMULATE_D parameter, and supply an input value. Note that you cannot enable the SIMULATE_D parameter when the LSDI block is running in a physical Logic Solver card.

You must configure the LSDI block completely to successfully download and use for simulation. To do this:

  1. Enable a channel in the simulated Logic Solver card.

  2. Define the channel type as Discrete Input.

  3. Assign the DST to the LSDI block's IO_IN parameter.

  4. Save and download the module.

You cannot download a simulated Logic Solver card if that card has SIS modules which contain incompletely configured LSAI and LSDI blocks.

To change a value from Control Studio Online, open the SIMULATE_D properties dialog and set a simulate value and status.

When SIMULATE_D is enabled, the value and status of the SIMULATE_D parameter become the value and status of FIELD_VAL_D.

Field Value Processing

You can select the Invert input option (IO_OPTS) to process FIELD_VAL_D:

  • Invert

When Invert is selected a NOT is performed on FIELD_VAL_D and the resulting value is copied to PV_D and OUT_D.

Filtering

Filtering in an LSDI function block is performed with on and off delays. FIELD_VAL_D must be on (or off) for PV_FTIME without changing before the block passes a change to PV_D.