HP VXI 75000 C Series, Руководство пользователя и программирования SCPI

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140 Algorithm Language Reference Chapter 5
Intrinsic Functions
and Statements
The following functions and statements are provided in the HP E1415’s
Algorithm Language:
Functions:
abs(expression) return absolute value of expression
max(expression1,expression2) return largest of the two expressions
min(expression1,expression2)
return smallest of the two expressions
Statements:
interrupt() sets VXI interrupt
writeboth(expression,cvt_loc) write expression result to FIFO
and CVT element specified.
writecvt(expression,cvt_loc) write expression result to CVT
element specified.
writefifo(expression) write expression result to FIFO.
Program Flow
Control
Program flow control is limited to the conditional execution construct using
if and else, and return. Looping inside an algorithm function is not
supported. The only "loop" is provided by repeatedly triggering the
HP E1415. Each trigger event (either external, or internal Trigger Timer)
executes the main() function which calls each defined and enabled
algorithm function. There is no goto statement.
Conditional Constructs
The HP E1415 Algorithm Language provides the if-else construct in the
following general form:
if (expression) statement1 else statement2
If expression evaluates to non-zero statement1 is executed. If expression
evaluates to zero, statement2 is executed. The else clause with its associated
statement2 is optional. Statement1 and/or statement2 can be compound
statement. That is { statement; statement; statement; ... }.
Exiting the Algorithm
The return statement allows terminating algorithm execution before
reaching the end by returning control to the main() function. The return
statement can appear anywhere in your algorithm. You are not required to
include a return statement to end an algorithm. The translator treats the end
of your algorithm as an implied return.
Data Types
The data type for variables is always static float. However decimal constant
values without a decimal point or exponent character (".", "E", or "e"), as
well as Hex and Octal constants are treated as 32-bit integer values. This
treatment of constants is consistent with ANSI ’C’. To understand what this
can mean you must understand that not all arithmetic statements in your
algorithm are actually performed within the HP E1415’s DSP chip at
algorithm run-time. Where expressions can be simplified, the HP E1415’s
translator (a function of the driver invoked by ALG:DEF) performs the
arithmetic operations before downloading the executable code to the
algorithm memory in the HP E1415. For example look at the statement;
a = 5 + 8;