Memory Map; Octal Numbering System; Discrete And Word Locations; V-Memory Locations For Discrete Memory Areas - Automationdirect.com DirectLOGIC DL205 Series User Manual

Memory Map

With any PLC system, you generally have many different types of information to process.
This includes input device status, output device status, various timing elements, parts counts,
etc. It is important to understand how the system represents and stores the various types of
data. For example, you need to know how the system identifies input points, output points,
data words, etc. The following paragraphs discuss the various memory types used in the
DL205 CPUs. A memory map overview for the DL230, DL240, DL250–1 and DL260
CPUs follows the memory descriptions.

Octal Numbering System

All memory locations or areas are numbered in Octal
(base 8). For example, the diagram shows how the
octal numbering system works for the discrete input
points. Notice the octal system does not contain any
numbers with the digits 8 or 9.

Discrete and Word Locations

As you examine the different memory types, you'll
notice two types of memory in the DL205, discrete
and word memory. Discrete memory is one bit that
can be either a 1 or a 0. Word memory is referred to as
V memory (variable) and is a 16-bit location normally
used to manipulate data/numbers, store data/numbers,
etc. Some information is automatically stored in V-
memory. For example, the timer current values are
stored in V-memory.
V–Memory Locations for Discrete Memory Areas
The discrete memory area is for inputs, outputs, control relays, special relays, stages, timer
status bits and counter status bits. However, you can also access the bit data types as a V-
memory word. Each V-memory location contains 16 consecutive discrete locations. For
example, the following diagram shows how the X input points are mapped into V-memory
locations.
X17
Bit #
15
These discrete memory areas and their corresponding V-memory ranges are listed in the
memory area table for the DL230, DL240, DL250–1 and DL260 CPUs in this chapter.
16 Discrete (X) Input Points
X16 X15 X14 X13 X12 X11
14 13 12 11 10 9
Chapter 3: CPU Specifications and Operations
X0 X1
X10 X11 X12 X13 X14 X15 X16 X17
Discrete – On or Off, 1 bit
Word Locations – 16 bits
0 1 0 1 0 0 0 0 0 0 1 0 0 1 0
X10 X7 X6 X5 X4 X3
8 7 6 5 4 3
DL205 User Manual, 4th Edition, Rev. B
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_
X7 X17 Y7
X2 X3 X4 X5 X6 X7
X0
X2 X1 X0
2 1 0 V40400
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