05 chapter03 03_memory_structure_slc500_fa14
DESCRIPTION
Chapter 03 Introduction to PLC Programming Slide set 03TRANSCRIPT
Chapter 03 Sect. 3-4, 3-5, 3-5-1, 3-5-3, 3-6, 3-6-2, 3-6-3, 3-7, 3-7-1, 3-9, 3-10PLC/PAC Memory Structure and Addressing
Memory Structure & Organization
As mentioned previously, there are three basic types of memory structures and organizations: Address-based memory Tag-based memory Combination of Address/Tag-based memory
Rack-Based Memory
Representation of most rack/slot address-based PLCs.
Represented by a two drawer file cabinet.
One drawer for data files
One drawer for program files
James A. Rehg, Glenn J. Sartori, Programmable Logic Controllers, 2nd Edition, Pg. 85
Program Memory
The user program accounts for most of the memory in a PLC system.
Program files contain the logic that controls the machine operation. This logic consists of instructions that are programmed in ladder logic format.
James A. Rehg, Glenn J. Sartori, Programmable Logic Controllers, 2nd Edition, Pg. 85
Memory Addressing
A memory address is a location within the PLC memory where information is stored.
The Allen Bradley SLC500 series PLC uses an alpha numeric sequence separated by delimiters that specifies the:
Type of data (bit level or word level) Slot location of an I/O module in a rack when
addressing field I/O Word number in memory, (Word is also referred to as
an element) Input or output number for field I/O and bit number for
internal coils and contacts.
AB SLC500 Slot Locations
Slot 0 Slot 1 Slot 2 Slot 3 Slot 4 Slot 5 Slot 6
AB SLC500 I/O Address Format
I1:4.0/4
File typeFile number
File delimiter
Slot or element number
Word delimiter
Word number
Bit delimiter
Bit or terminalnumber
States: Input module in slot 4 IN4
O0:5.0/13 – Output module, slot 5, OUT13
AB SLC500 I/O Address Format
I1:4.0/4
File typeRequired
File numberOnly required when a
user defined file is being specified.
File delimiterRequired
Slot or element numberRequired
Word delimiterOnly required when
specifying a word number.
Word numberOnly required if pointing to a word other than word zero.
Defaults to word zero.
Bit delimiterOnly required when
addressing to “bit level”.
Bit or IN/OUT numberOnly required when addressing to “bit
level”.
This address can be rewritten as: I:4/4
SLC500 Default File Types
File Type Identifier File NumberOutput O 0
Input I 1
Status S 2
Bit B 3
Timer T 4
Counter C 5
Control R 6
Integer N 7
Floating Point * F 8
* Available in SLC-5/03 OS301, OS302 & SLC-5/04 OS400, OS401 & SLC-5/05 processors
SLC500 User Defined File Types
File Type Identifier File NumberBit B 91 - 255
Timer T 91 - 255
Counter C 91 - 255
Control R 91 - 255
Integer N 91 - 255
Floating Point * F 91 - 255
String * St 91 – 255
ASCII * A 91 - 255
Special Note1 Computer Interface File (CIF)1 9
• Available in SLC-5/03 OS301, OS302 & SLC-5/04 OS400, OS401 & SLC-5/05 processors
1 The only file that data can be xmitted/received to/from non-IP devices
Data Files in the Project Window
RSLogix 500 Default Files LogixPro Default Files
Input/Output Elements
I/O modules are considered to be one element (word) files. In the SLC500 series this means that a 16-point module uses one 16-bit word and in the ControlLogix series it uses 16-bits of one 32-bit word. An SLC500, 32-point module will use two 16-bit words (32-bits) and a ControlLogix will use one, 32-bit word.
0 0 0 0 0 0 0 00 0 0 0 0 0 0 0
15 10 9 8 7 6 5 4 3 2 1 014 13 12 11
0 0 0 0 0 0 0 00 0 0 0 0 0 0 00 0 0 0 0 0 0 00 0 0 0 0 0 0 0
0
1
2
Bit numbers (16-bit word(s))
Element or word number
Addressing Input/Output Elements (Words (16-bit PLC))
I/O addressing for modules that have 8-points, 16-points & 32-points. To address bit-9 of the input module in slot-1; I1:1.0/9 or I:1/9 To address bit-5 of the input module in slot-3; I1:3.0/5 or I:3/5 To address bit-14 of the input module in slot-6; I1:6.0/14 or I:6/14 To address bit-6 in the second word of the module in slot-6; I1:6.1/6 or I:6.1/6 or I:6/22
16-point module in slot-1Requires 1-word
16-point module in slot-4Requires 1-word
8-point module in slot-3Requires 1-word
only uses the lower byte
32-point module in slot-6Requires 2-word
Word-0 for the first 16-bitsWord-1 for the last 16-bits
Screen shot of an input data table from RSLogix 500
Bit File, File #3
File #3 is the bit file and is designated with the letter ‘B’.
One application for the bit file is for internal control relays where each bit can be a relay coil.
In the SLC500 the bit file contains 256, 16-bit words for a total of 4,096 bits.
Each bit, when used as a coil, can have an unlimited number of normally open and/or normally closed contacts programmed to it.
Addressing the Bit File
The bit file is addressed using the same address structure as the Input/Output file.
The differences are: The letter used for the file designator will now be
the letter ‘B’ There is no slot number. What was the slot
number, now becomes the word number within the file.
The following address references word 0, bit 0, of the default bit file.
B3:0/0 or B:0/0
Addressing the Bit File
Addressing Bit 12 in word 255 of the default bit file would be:
B3:255/12 or B:255/12 Addressing Word 42, bit 7, of the user
defined bit file number 12 would be:
B12:42/7In this example the file number is required because it is a user defined file.
Input Interaction
Limit switch is open, or off. It is wired to IN7 of the input
module. If this input module is in slot-1 of the PLC rack, the switch status will be stored in bit-7 of the word associated with slot-1.
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Com
2
4
5
6
3
1
0
7
L1
02040506 03 0107 0010121314 11 0915 08
Word I:1.0
LimitSwitchInput
AddressI1:1.0/7
Input Interaction
Limit switch is closed, or on. It is wired to IN7 of the input
module. If this input module is in slot-1 of the PLC rack, the switch status will be stored in bit-7 of the word associated with slot-1.
0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0
Com
2
4
5
6
3
1
0
7
L1
02040506 03 0107 0010121314 11 0915 08
Word I:1.0
LimitSwitchInput
AddressI1:1.0/7
Output Interaction
The logic of the control program evaluated bit-5 of the output module in slot-2 as false, or off.
The output device wired to OUT5 of the output module in slot-2 will turn off.
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Com
2
4
5
6
3
1
0
7
L1
02040506 03 0107 0010121314 11 0915 08
Word O:2.0
OutputAddressO0:2.0/5
Output Interaction
The logic of the control program evaluated bit-5 of the output module in slot-2 as true, or on.
The output device wired to OUT5 of the output module in slot-2 will turn on.
0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0
Com
2
4
5
6
3
1
0
7
L1
02040506 03 0107 0010121314 11 0915 08
Word O:2.0
OutputAddressO0:2.0/5
SLC500 Basic Bit Level Instructions
Normally OpenExamine if Closed
XIC
Normally ClosedExamine if Open
XIO
Output CoilOutput Energize
OTE
Rung Comment
InstructionDescription
Address Symbol
AddressShown split withbit number at the
base of theinstruction
Bit number
Rung number
Default color scheme shown
ControlLogix Basic Bit Level Instructions
Normally OpenExamine if Closed
XIC
Normally ClosedExamine if Open
XIO
Output CoilOutput Energize
OTE
Rung Comment
InstructionDescription
Tag
Alias to theI/O module
Rung number
Modified color scheme shown
LogixPro Basic Bit Level Instructions
Normally OpenExamine if Closed
XIC
Normally ClosedExamine if Open
XIO
Output CoilOutput Energize
OTE
Rung CommentRestricted to
one line
Address SymbolThere is noinstructiondescription
AddressShown in-line.
RSLogix 500 canbe configured to
display the addressin-line.
Rung number
Default color scheme shown
Processor Scan
The processor evaluates the program logic similar to the way we would evaluate electromechanical ladder logic:
Top to bottom, left to right, one rung at-a-time. This process is called Processor Scan or
simply Scan.
Read InputDevice Status
Solve the control program logic based upon the status of the input devices
Update the status of
the output devices
Housekeeping and
communications
Scan Cycle
Read input status
Solve the control program and turn
internal coils on/off
Update the outputs
Housekeeping and
Communications
Other One Element Files (16-bit PLC)
The input and output files are not the only 1-element (1-word) files. The following files are also 1-element (1-word) files:
Status (file-2) Number of words in the file depends upon the processor type
Bit (file-3) 256, 16-bit words are available in each bit file Integer (file-7) 256, 16-bit words are available in each integer file
0 0 0 0 0 0 0 00 0 0 0 0 0 0 0
15 10 9 8 7 6 5 4 3 2 1 014 13 12 11
0 0 0 0 0 0 0 00 0 0 0 0 0 0 0
0 0 0 0 0 0 0 00 0 0 0 0 0 0 0
0
1
2
Bit numbers
Element or word number
Three or more Element Files (16-bit PLC)
Some file types in the Allen Bradley SLC500 series PLC require more than 1-word per instruction.
Timers, Counters and Control instructions are such files. Each timer, counter or Control instruction requires 3-words.
0 0 0 0 0 0 0 00 0 0 0 0 0 0 0
15 10 9 8 7 6 5 4 3 2 1 014 13 12 11
0
1
2
Element or word number. Word-0 will contain instruction status bits. Values stored in words-1 & 2 will depend upon the file type being addressed.
Bit numbers
Software Introduction Labs
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submit the electronic version of the file. (.rsl file)