Emerson manual Rosemount 848L, Reference Manual, 00809-0100-4696,Rev AA September

Rosemount 848L

Reference Manual

00809-0100-4696, Rev AA September 2004

The following characters are allowed in a logic equation:

•Uppercase and lowercase alphabet, case insensitive, used to specify functions

•Digits 0-9, used to specify channel numbers and unsigned integer constants

•Comma, used to separate parameters in a function parameter list

•Parentheses() used to define the extent of the parameter list of a function

•Semicolon; used to terminate an equation

•Space (not tab), ignored by parser, may be used to make an equation more readable but counts as a character

The following characters are specifically not allowed in a logic:

•The period (dot) character is not allowed. There are no decimal numbers.

•The unary minus (-) character is not allowed. There are no negative integers.

•The math operators (+, -, *, /, **) are not allowed, nor are symbols for any logic operators (&, , <, >, ...).

Functions must be from the list of Logic Functions below, and must have the specified number of parameters.

Channel Functions

The following functions read channel value and status. The number of instances of these functions is unlimited, except for PS. A channel value and status is set by the I/O processor at the beginning of an equation evaluation cycle, by the equations as they complete evaluation, or by macrocycle evaluations of any DO blocks attached to channels 9 through 16. The status of channels 9-16 is always good, even if the DO block has a bad status.

IN - The input hardware sets the values of channels 1-8. Configured DI blocks may specify these channels in order to read the specified hardware input. The value of an input may be referenced in an equation by the IN (i) function, where the channel number is placed between the parentheses. The range of ‘i’ is 1 to 8. Multiple references to any channel are allowed.

ICR, ICF - I/O samples are taken every millisecond, which is considerably faster than equation executions. It is possible for an input to turn on and turn off during an equation evaluation cycle, so that it would not be seen by an IN (i) function. Each input has a counter for transitions (rise or fall). A transition is based on the output of the debounce filter, not the raw input. Filtering can be set to zero. The counter is read and cleared at the beginning of each evaluation cycle. The method relies completely on the counter and does not use the latch configuration. The ICR (i) function is true for one evaluation cycle if a rising transition occurred, and its opposite ICF (i) is true for a falling transition.

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