The Smart HART Discrete Input (SHDI) function block accesses a single discrete input variable with status from a Wireless Discrete field device and makes the processed physical input available to other function blocks in either a binary format (OUT_D), or a named set output (OUT_STATE). The input variable is an enumerated named set that can take on any in the list of SHDI and SHDO named set codes. The value of OUT_D (0 or 1) is determined by comparing the input Named Set value to the TARGET_STATE enumerated value. If they compare, then the output is a 1, else a 0.
The Smart HART Discrete Input function block supports mode control, signal status, propagation, and simulation.
To support testing, you can enable simulation. This allows the measurement value to be supplied manually or from another block through the SIMULATE_IN_STATE input.
SIMULATE_IN_D is the simulated HART discrete input value with status the block uses when simulation is enabled. This can be any value from the list of SHDI and SHDO named set codes.
OUT_D is the translated binary output value and status.
OUT_STATE is the index to the text describing the states of a discrete for the value obtained from the transducer.
The following diagram shows the internal components of the Discrete Input function block.
