Yokogawa Touch Screen GP20 User Manual download pdf (Page 68)

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IM 04L51B01-01EN

1.5.3 Writing Expressions

Common Items

Follow the rules below when writing expressions.

• Use up to 120 characters to write expressions.

• The precedence of computing terms can be specified using parentheses.

• Specify channels in expressions using channel numbers.

Example: 0001, 0012, A001, C001

• The “0” in the top digit of I/O channel numbers (0101), math channel numbers (A001),

communication channel numbers (C010), constants (K), internal switch numbers (S), and

flags (F) can be omitted.

Examples: 101, A1, C10, K1, S1, F1

• The data of the previous scan is used in the computation for its own channel number and

channel numbers greater than its own channel number in the expression.

• Write special computations (HOLD, RESET, and CARRY) and conditional expressions at

the beginning of expressions.

Order of Precedence in Computations

The order of precedence of computation in expressions is as follows:

Type Computing Element

Function ABS(), SQR(), LOG(), LN(), EXP(), TLOG.MAX(), TLOG.MIN(), TLOG.

AVE(), TLOG.SUM(), TLOG.P-P(), CLOG.MAX(), CLOG.MIN(), CLOG.

AVE(), CLOG.SUM(), CLOG.P-P()

Special computation and

conditional expression

PRE, HOLD, RESET, CARRY, [a?b:c]

Power **

Logical negation NOT

Multiplication and division *, /

Addition and subtraction +, –

Greater than and less than .GT. (or >), .LT. (or <), .GE. (or >=), .LE. (or <=)

Equal and not equal .EQ. (or =), .NE. (or <>)

Logical product AND

Logical sum and exclusive

logical sum

OR, XOR

Limitations

The following limitations exists in expressions.

Type Limitations

TLOG Computation A computing element cannot be written inside the parentheses.

Only one TLOG computation can be specified in a single expression.

CLOG computation The number of channels that can be written in the parentheses is up to 30

channels.

A computing element cannot be written inside the parentheses.

Only one CLOG computation can be specified in a single expression.

PRE A computing element cannot be written inside the parentheses.

HOLD(a):b Can only be written at the beginning of an expression.

Only one HOLD computation can be specified in a single expression.

RESET(a):b Can only be written at the beginning of an expression.

Only one RESET computation can be specified in a single expression.

CARRY(a):b Can only be written at the beginning of an expression.

Only one CARRY computation can be specified in a single expression.

Only TLOG.SUM can be written in b.

Conditional equation

[a?b:c]

RESET, CARRY, or HOLD cannot be written to a, b, or c.

Other computing elements cannot be combined (example: [a?b:c]+0001).

However, conditional equations can be specified for a, b, and c.

1.5 Configuring Math Channels

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Yokogawa Touch Screen GP20 User Manual Page 68

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