National Instruments FP-3000 - Manual (Page 59)

Chapter 4 Block Reference
© National Instruments Corporation 4-7 FieldPoint FP-3000 User Manual
• 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.