FST Register Parameters

The FST Register creates or monitors a Function Sequence Table Register point. FSTs allow you to define and perform a set of specific actions to be taken when a set of conditions exists. FSTs can be written specifically for applications that require special control features, such as logic sequencing capability. For example, an FST may be written that is used as an emergency shutdown control when dangerous flow occurs.

An FST defines the input-to-output relationships in the ROC or FloBoss through a set of user-selected instructions, called functions. These functions, which define the specific actions to be performed, are executed in their specified sequence. The normal top-to-bottom sequence may be altered by certain decision-making functions, such as if/then statements, loops, or comparison values that you establish. Each FST may consist of as many functions as can fit into the memory reserved for the FSTs.

Reserved memory is pre-determined by the ROC or FloBoss. An FST is built from a library of commands that provide mathematical and logical operations, database access operations, testing, and branching operations, and control-related operations.

Each FST contains ten Registers. By default, FSTs automatically write and read all results to and from the Results Register (RR) unless you manually tell the FST in the Argument fields to store or acquire the value from FST Registers R1 to R10. The Registers can store calculated or manually- entered values and can pass data from one table to another. That is, the FST can write values to the FST Register and the FST can also read the values stored in the FST Register storage points. These Registers may be read from, or written to, any FST configured for the ROC or FloBoss and are referred to as Register R1 through Register R10.

The FST Registers can be used to store temporary values acquired from a calculated process that was polled by the ROC or FloBoss. You may also enter a static value in a FST Register and read that value into an FST to set a process to a specific value.

1. Select Configure > Control > FST Register. Refer to Figure B-1.

Figure B-1. FST Parameters

Rev 05/03 FST Editor B-3 3. Enter the Tag as a 10-character name identifying the FST Register point.

4. Select FST Status Enabled for the FST associated with this FST Registers point. You can turn the associated FST on or off by selecting or deselecting the correct checkbox and clicking Apply.

5. Enter the Register R1 to R10 ten floating-point registers are used for storage among all FSTs in the ROC and FloBoss. The FST Registers can store calculated or manually-entered values and can pass data from one table to another. These Registers may be read from, or written to, by any FST and are referred to as Register R1 to Register R10.

B.2.1 FST Advanced

Use FST Advanced options to expand FST capabilities.

1. Select Configure > Control > FST Register.

2. Click the Advanced tab. Refer to Figure B-2.

Figure B-2. FST Parameter Advanced

The Timer #1 to #4 values are determined by the FST. These four timers, when set greater than “0,” decrement by 1 every 100 milliseconds. For the FloBoss 103 , the timers are decremented once every second. When the timer reaches “0,” the FST branches to the label specified in the Timer function. The sequence of functions is executed at the frequency defined in the Timer parameter fields.

3. Set the Misc #1 to #4 unsigned integers (8-bit bytes with valid decimal values of 0 to 255) that are used for global storage by the FST.

4. Set the Exec Delay between the execution of successive FST command steps. The default is 0 seconds; the minimum delay you can specify is 0.1 seconds (1.0 seconds in the FloBoss 103).

5. Set the Result Reg as the Results Register. The Results Register is a floating point value that is passed between functions. As the sequence of functions executes, two memory locations store intermediate results from one function to the next. The Results Register (RR), stores a floating-point or analog value, called the Signal Value Analog (SVA). Depending on the function, the Results Register and the Compare Flag (CF) may be loaded, stored, tested, modified, or left unchanged.

6. Set the Compare Flag (CF) as an 8-bit integer representing the numbers 0 through 255. The Compare Flag stores a discrete value called the Signal Value Discrete (SVD). Depending on

B-4 FST Editor Rev 05/03

the function, the Results Register and the Compare Flag may be loaded, stored, tested, modified, or left unchanged.

7. Set the Mesg #1 and Mesg #2 30-character field for storing a message. The message can display on the Local Display Panel.

8. Set the Code Size as the number of bytes used by the FST, equivalent to the end pointer position minus the start pointer position. The maximum value for a FloBoss 500-Series is 4000; maximum for a FloBoss 103 is 3000.

Bytes indicates the size of the next function to be executed.

Code Pointer Byte is the location in ROC memory of the next function to be executed. There are 0 to 7999 storage locations for functions in the ROC. One storage location is used for each byte that makes up the function.

NOTE: Use Monitor functions within the FST Editor to monitor these options.