226 Rockwell Automation Publication 520-UM001K-EN-E - August 2021
Appendix E Encoder/Pulse Train Usage and Position StepLogic Application
left of the decimal (whole number) and d379 [Encoder Speed F] is the number
to the right of the decimal (the portion less than 1).
d388
, d389 [Units Traveled x] indicate the current position of the system in
terms of units away from Home. Parameter d388 [Units Traveled H] is the
number value to the left of the decimal (whole number) and d389 [Units
Traveled L] is the number to the right of the decimal (the portion less than 1).
d387
[Position Status] indicates the status of the positioning functions. The
indication bits are:
Bit 0 “Dir Positive” indicates the current direction the drive has moved
from Home.
Bit 1 “At Position” indicates whether the drive is at its commanded
position. If the drive is within A564
[Encoder Pos Tol] of the
commanded position, this bit will be active.
Bit 2 “At Home” indicates whether the drive is at Home. If the drive is
within A564
[Encoder Pos Tol] of “Home”, this bit will be active.
Bit 3 “Drive Homed” indicates whether the drive has been homed
since power up. This bit will be active once the drive has been homed
either manually or automatically. It will remain active until the next
power down.
Use Over Communications If 8 steps are not adequate for the application or if dynamic program changes
are required, many of the positioning functions can be controlled through an
active communication network. The following parameters will allow this
control.
C121
[Comm Write Mode]
Repeated writes to parameters over a communication network can cause
damage to the drive EEPROM. This parameter allows the drive to accept
parameter changes without writing to the EEPROM.
C122
[Cmd Stat Select]
Selects velocity-specific or position/fibers-specific Command and Status Word
bit definitions for use over a communication network.
A560
[Enh Control Word]
This parameter allows many of the positioning functions to be completed
through parameter control using an explicit message. This allows the
operation over communications instead of with hardware inputs. The bits
have the same functions as the digital input options of the same name. Options
relating to positioning are:
Bit 0 “Home Limit” indicates the drive is at the home position.
IMPORTANT
Parameter values set prior to setting 1 “RAM only” are saved in RAM.
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