National-instruments FP-3000 Manual de usuario descargar pdf (Pagina 59)

Chapter 4 Block Reference

• C-language style program constructs—Program statements that define

the logic of the expression with the use of conditional statements,

variable assignments, etc. Each valid statement ends with a

semi-colon.

• Empty lines for vertical spacing—You can add empty lines to improve

readability.

Program Constructs

Program constructs in the Expression block are C-language like. They are

comprised of keywords, symbols, constants, operators, conditional

statements for flow control, and delimiters (for the most part).

Reserved Symbols

• a_in_0, a_in_1, a_in_2, a_in_3, a_in_4, a_in_5, a_in_6, a_in_7

These symbols correspond to the EXPR block’s analog input

parameters A_IN_0, A_IN_1, A_IN_2, A_IN_3, A_IN_4, A_IN_5,

A_IN_6, and A_IN_7, respectively.

• d_in_0, d_in_1, d_in_2, d_in_3

These symbols correspond to the EXPR block’s discrete input

parameters D_IN_0, D_IN_1, D_IN_2, and D_IN_3, respectively.

• a_state_0, a_state_1, a_state_2, a_state_3

These are symbols for the EXPR block’s parameters that you can use

as local variables in an expression. They correspond to the EXPR block

parameters A_STATE_0, A_STATE_1, A_STATE_2, and

A_STATE_3, respectively.

• a_out_0, a_out_1, a_out_2, a_out_3

These symbols correspond to the EXPR block’s analog output

parameters A_OUT_0, A_OUT_1, A_OUT_2, and A_OUT_3,

respectively.

• d_out_0, d_out_1, d_out_2, d_out_3, d_out_4, d_out_5, d_out_6,

d_out_7

These symbols correspond to the EXPR block’s discrete output

parameters D_OUT_0, D_OUT_1, D_OUT_2, D_OUT_3,

D_OUT_4, D_OUT_5, D_OUT_6, and D_OUT_7, respectively.

• x_time

Provides read-only access to the FP-3000’s sense of application time

in the Expression block. Application time is expressed in the number

of seconds since January 1, 1972.

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National-instruments FP-3000 Manual de usuario Pagina 59