Rockwell Automation 1772-LV Mini-PLC - 2/15 Programmable Controller (Series B) Programming and Operations - Manual (Page 207)

Glossary
Appendix B
BĆ14
Read
1) Accessing of data from a storage device such as memory, magnetic tape, etc.
2) Transfer of data between devices, such as between a peripheral device and a
computer.
Read/Write Memory
A memory in which data can be placed (write mode) or accessed (read mode).
The write mode destroys previous data, read mode does not alter stored data.
Remote I/O PC
A type of programmable controller in which some or all of the I/O chassis are
mounted in separate enclosures. Any remote I/O chassis may be located either
close to the PC processor or as far away as 5000 or 10,000 cable feet, depending
on the specific hardware.
Remote Mode Selection
A feature which allows the user to select or change processor modes by means
of a program panel from as far away as 5000 cable feet.
Report
An application data display or printout containing information in a
user-designed format. Reports include operator messages, part records,
production lists, etc. Initially entered as messages, reports are stored in a
memory area separate from the user’s program.
Report Generation
The printing or displaying of user-formatted application data by means of a data
terminal. Report generation can be initiated by means of either the user’s
program or a data terminal keyboard.
Retentive Output
An output that remains in its last state (on or off) depending on which of its two
program rungs (one containing a latch instruction, the other an unlatch) was the
last to be true. The retentive output remains in its last state while both rungs are
false. It also remains in its last state if power is removed from, then restored to,
the PC (Contrasted with a non-retentive output which is continuously controlled
by single rung.)
Retentive Timer
A PC instruction which accumulates the amount of time, whether continuous or
not, that the preconditions of its rung are true, and controls one or more outputs
(by means of other rungs) after the total accumulated time is equal to the
programmed time. Whenever the rung is false, the accumulated time is
retained. Moreover, if the outputs have been energized, they remain on. Also,
the accumulated time and energized outputs are retained if power is removed
from, then restored to, the PC. A separate rung, containing a retentive timer
reset instruction, must be programmed in order to reset the accumulated time to
zero and turn off the outputs.