Allen-Bradley LOGIX 5000 Reference Manual page 296

Chapter 2 Drives
296
Execution
Function Block
Condition
Prescan
Tag.EnableIn is false
Tag.EnableIn is true
Instruction first run
Instruction first scan
Postscan
Structured Text
Condition/State
Prescan
Normal Execution
Postscan
Example
In most coordinated drive applications, a master reference commands line speed
for an entire group of drives. As various references are selected, the drives cannot
be presented with "step" changes in speed reference because differences in load
inertia, motor torque, and tuning would not allow the individual drive sections to
react in a coordinated manner. The SCRV instruction is designed to ramp and
shape the reference signal to the drive sections so that acceleration, deceleration,
and jerk, (derivative of acceleration,) are controlled. This instruction provides a
mechanism to allow the reference to the drives to reach the designated reference
setpoint in a manner that eliminates excessive forces and excessive impact on
connected machinery and equipment.
Rockwell Automation Publication 1756-RM006K-EN-P - November 2018
Function Block Action
EnableIn and EnableOut bits are cleared to false.
EnableIn and EnableOut bits are cleared to false.
EnableIn and EnableOut bit bits are set to true
The instruction executes.
N/A
Clear previous scan data.
EnableIn and EnableOut bits are cleared to false
Action Taken
See Prescan in the Function Block table.
See Tag.EnableIn is true in the Function Block table.
See Postscan in the Function Block table.