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HVI Flowcharts

Flowcharts represent a program or execution sequence by means of instructions and flow-control boxes (called statements), and timing arrows. Statements define HVI actions, while arrows define the execution flow and timing. All these elements are explained throughout this section.

Timing Arrows

Timing Arrows define and inform about the time between statements. Therefore, the user may thing as if statements do not take any time and all the timing information is given by the Timing Arrows. There are two kind of arrows:

• Solid Arrows: Normal arrows which connect statements. They can have a well defined time at programming time, or they can show a time uncertainty with a question mark (e.g. Figure 4).
• Dashed Arrows: The dashed arrows show a time uncertainty due to a synchronization recovery (the modules must wait for other modules). These arrows appear before a (Synchronized Flow-Control Statements) when there has been a desynchronization event (e.g.  after Wait Statements, loops with variable cycles, etc.). For dashed arrows, the user can set the minimum time, but the maximum its only defined at runtime.

Synchronized Flow-Control Statements

Flow-control statements are elements that control the HVI execution flow. Synchronized Flow-Control Statements are particular Flow- control Statements that are executed in all modules at the same time.

Start

Every flowchart begins with a Start Statement (Figure 3), which is in fact a Synchronized Junction Statement (Figure 4), This statement ensures that all the hardware modules in an HVI start the execution fully synchronized.

End

The End Statement indicates the end of the HVI execution, and must be placed by the user to terminate the HVI properly (Figure 3).

Synchronized Junction

A Synchronized Junction Statement is an element that can be used as a destination for conditional jumps (Synchronized Conditional).

Figure 3: Flowcharts of two modules, showing the Start and the End Statements

Figure 4: A Synchronized Junction Statement (ellipse-shaped element) can also be used to synchronize flowcharts

Synchronized Conditional

M3601A allows the user to perform conditional jumps to control the HVI execution flow, enabling the implementation of ultra-fast decision making, loops, etc.

A synchronized jump in the execution flow requires two elements:

1. Synchronized Conditional Statement, which is the element that evaluates the condition and performs the jump
2. Destination element.

The latter can be the statement right below the conditional or a Junction Statement placed anywhere in the flowchart (Figure 5).

Master and slave synchronized conditionals: In a Synchronized Conditional Statement, the decision is taken by only one of the modules (called master), and all the others (slaves) will comply with the same conditional result.

Local Flow-control Statements

Flow-control Statements are elements that control the HVI execution flow. Local Flow-Control Statements are particular Flow-control Statements that are executed only in one module, without affecting the execution flow of other modules.

Figure 5: A Synchronized Conditional Statement (diamond-shaped element) jumps to a Junction Statement (ellipse-shaped element) in two modules exactly at the same time. The GUI maintains the synchronization by adjusting automatically the time of the last Timing Arrow. The solid dot in the arrow below the Conditional indicates the jump under a FALSE condition evaluation, while the side branch indicates the jump under a TRUE condition evaluation.

If Block

The If Block Statement is the classical ”if/else structure” available in any programming language. The If Block provides two operation options:

• Branch Synchronization Forced: the total time of the two branches (if and else) is forced to be equal, and therefore the execution time is well defined (does not depend on the branch). In this case, the If Block Statement does not desynchronize.
• Branch Synchronization Unforced: the total time of the two branches (if and else) can be different, and therefore the execution time may be defined only at runtime (when the branch is decided). If this is the case, the If Block Statement produces desynchronization.

Figure 6: An If Block with equal timing in both branches does not desynchronize

Figure 7: An If Block with different timing in both branches desynchronizes, as it it shown in the flowchart of the other modules (right)

For Block

The For Block Statement is the classical ”for loop structure” of any programming language. The user can choose which local register (M3601A HVI Design Environment Basics) is used for the loop index, and the exit value (number of loops).

Figure 8: For Block Statement

While Block

A While Block Statement is the classical ”while loop” structure of any programming language. The execution loops while a condition is fulfilled.

Figure 9: While Block Statement

Wait

The Wait Statement can be configured to wait for two different events:

• Variable Time: It waits the amount of time defined in a local register. The time unit in the register is defined in tens of nanoseconds.
• PXI Trigger: It waits until the selected PXI trigger has the desired value (On or Off).

Figure 10: Wait Statement with an undefined execution time (left flowchart). This timing uncertainty can be seen in the arrow below the Wait. Please note that this also produces a desynchronization, which is shown with the dashed arrows above the Synchronized Junction. The latter performs a synchronization recovery in both modules (left and right).

Instruction Statements

Instruction statements describe the main actions of an HVI, without altering the execution flow directly.

Built-in Instructions

Built-in instructions are the main execution statements of an HVI. There are two kind of instructions statements: module-specific, e.g. an instruction to change the amplitude of an Arbitrary Waveform Generator (AWG) (built-in module-specific instructions are described in the User Guide of the module), and universal instruction statements, like arithmetic operations, etc., which are available in all Keysight compatible modules with -HV1 programming enabled option.

Instruction Execution Latency: Instructions are triggered according to the statement timing within the flowchart, however each module-specific instruction has its own execution latency. Check the module datasheet for latency values.

Built-in Instructions: Universal

This chapter describes the universal instruction statements available in all modules.

MathAssign (D=S)

This function copies the value of the source parameter (S) into the destination variable (D).

Parameters

MathArithmetics (R=A[+-*/]B)

This function subtracts, adds, multiplies or divides the values of the operands A and B, writing the result in R.

Parameters

MathLogic (R=A [op] B)

This function performs a logic operation with the values of the operands A and B, writing the result in R.

Parameters

MathSQRT (R=sqrt(A))

This function performs the square of the source parameter (A), writing the result in R.

Parameters

HVIport

This function performs a read or write operation on port HVI available in M3602A.

Parameters

Built-in Instructions: Module-specific

Module-specific instructions are explained in the user guides of the corresponding hardware modules.

External Variable Access

This statement writes or reads into/from a variable of another module (M3601A HVI Design Environment Basics).