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Glossary
372 SPU 780 01EMAN May 2002 311
Distributed I/O
(DIO)
One of four major architectures for input/output systems (also see Local I/O,
Remote I/O, and Peer-to-peer Communications). I/O that is installed away from
the PLC over a wide area and communicates with it through a Modbus Plus network.
One Quantum controller can support up to three distributed I/O networks, each with
up to 64 drops. The local rack houses a DIO processor for each network, which sets
the network’s head number.
Documentation A description of a controller’s memory, logic, and configuration. The descriptors,
short comments, long comments, and page titles within a database.
Documentation
Editor
The editor in which descriptors, short comments, long comments, and page titles
can be entered and modified.
Double Precision A 32-bit format which uses two registers to store numerical values.
Drop A group of I/O cards physically connected together as an I/O network. A controller
reads information from the drop, solves logic, then writes results to the drop in one
segment of ladder logic. The Segment Scheduler controls the order in which drops
are serviced.
Duplicate Coil An output coil address which has been assigned to more than one coil.
EEPROM Electrically Eraseable Programmable Read-Only Memory.
Element A ladder logic instruction such as a coil, timer, or short.
Enable To allow a PLC, based on the logic programmed into it, to update the state of a coil
or input.
Equation
Network
A special section of logic that lets the programmer solve regular mathematical
equations within the network. Not supported by every controller.
Exponential
Notation
A format for numbers based on powers of 10. For example, +1.35E-4 indicates 1.35
multiplied by 10 to the power of -4 (i.e. with an exponent of -4), which works out to
0.000135.
Extended
Memory
Extra register memory available for some models of 984/584 controllers. It is
accessed through the XMRD and XMWT functions.
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