Installation manual

Publication 1747-RM001G-EN-P - November 2008
4-22 Math Instructions
Instruction Operation
When the rung state is true all parameters are validated to be in range. If the
parameters are valid, the ramp function places the calculated output value in
the destination register. The parameters are validated for every scan when the
rung state is true. When the Ramp instruction is scanned and the rung state is
true, the current time is updated, the destination value is calculated, and done
condition is checked.
When the rung state is false, the current time is not updated and the
destination value is not calculated. When the rung state sees another false to
true change the current time is determined from the last updated position. An
accuracy of +/- one unit (1 second or 0.01 seconds depending on ramp) or
one scan, whichever is larger, can be expected for a false-to-true or
true-to-false rung transition.
The Ramp instruction is retentive. If a Ramp instruction is executing when a
power cycle occurs, the instruction continues to operate starting with the last
updated position. The accuracy is limited to one unit or one scan, whichever is
larger. Ramp instructions can be cascaded.
ATTENTION
Changing words 1 through 4 during instruction
execution causes loss of resolution of one unit of
measurement (1 second or 0.01 seconds depending
on ramp). If these values are modified during
execution the destination value automatically
recalculates for the new value on the next scan.
ATTENTION
Modification of words 5 and 6 could result in
unpredictable operation, possibly causing equipment
damage and/or injury to personnel.