Allen Bradley Plc Slot Numbering

Allen Bradley Plc Port Number
Allen Bradley Plc Slot Numbering Chart

When PLC rack is inserted in PLC manager, slots startwith number 1. If I use Allen-Bradley PLSs, the module numbers start with 0. So all the addressing is screwed up. Is it possible to change module numbers? The 2 means the input module is in slot 2 of the rack (the third slot from the left). The 1 means it is channel 1 (the second input channel on that module). NOTE: When programming a MicroLogix PLC, slot numbers do not apply since all the I/O is built in to the controller. All I/O references use 'slot 0' in MicroLogix project. For example I:0/1.

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Introduction

Allen Bradley Plc Port Number

There are two distinct ranges of Allen Bradley PLC Devices:

Model Types	Summary
SLC-500, MicroLogix, PLC-5.	These models are configured using ladder logic and store data in files. Tags in Fernhill SCADA are mapped to locations in the data files. The File Data Address Format defines which location in the PLC is mapped to a Fernhill SCADA Tag. Fernhill SCADA uses this tag format when the PLCType Configuration Property is set to 0 (Micrologix, SLC and PLC-5).
ControlLogix, CompactLogix.	These models implement the IEC 61131-3 standard and each data item is assigned a unique variable name. Tags in Fernhill SCADA are mapped to variables in the PLC program. The Variable Reference Format defines which variable in the PLC is mapped to a Fernhill SCADA Tag. Fernhill SCADA uses this tag format when the PLCType Configuration Property is set to 1 (ControlLogix or CompactLogix).

File Data Address Format

This File Data Address Format is used with MicroLogix, SLC and PLC-5 range of PLC Devices.

The File Data Address Format is a string that defines the location of data in a file based Allen Bradley PLC. The format of the string is:

Xf:e.w/b

Where:

X is the file type.
f is the optional file number.
e is the element number.
w is the optional word offset.
b is the optional bit offset.

File Type

Data in Allen Bradley PLC Devices is stored in files. For example there are separate files for Inputs, Outputs, Status Bits, Timers, Counter, Integers and so on. Some file types are fixed, for example there can only be one file each for Inputs, Outputs and Status Bits. Other files are more flexible, for example there can be multiple Integer files.

File	Type	Notes
O	Outputs	If used, the File Number must be 0. The Element Number sets the I/O slot. The Word Offset sets the word offset within the I/O slot. The Bit Offset sets the bit number (0-15).
I	Inputs	If used, the File Number must be 1. The Element Number sets the I/O slot. The Word Offset sets the word offset within the I/O slot. The Bit Offset sets the bit number (0-15).
S	Status	If used, the File Number must be 2. The Element Number sets the status word. The Bit Offset sets the bit number (0-15).
B	Bit	The File Number sets which bit file to use (3, 9-255). If not used, the File Number is 3. The Element Number sets the word. The Bit Offset sets the bit number (0-15).
T	Timer	The File Number sets which timer file to use (4, 9-255). If not used, the File Number is 4. The Element Number sets the timer index. The Word Offset sets the word offset within the timer (0-2). The Bit Offset sets the bit number (0-15).
C	Counter	The File Number sets which counter file to use (5, 9-255). If not used, the File Number is 5. The Element Number sets the counter index. The Word Offset sets the word offset within the counter (0-2). The Bit Offset sets the bit number (0-15).
R	Control	The File Number sets which control file to use (6, 9-255). If not used, the File Number is 6. The Element Number sets the control index. The Word Offset sets the word offset within the control (0-2). The Bit Offset sets the bit number (0-15).
I	Integer	The File Number sets which integer file to use (7, 9-255). If not used, the File Number is 7. The Element Number sets the word. The Bit Offset sets the bit number (0-15).
F	Float	The File Number sets which float file to use (8-255). If not used, the File Number is 8. The Element Number sets the float index.
ST	String	The File Number sets the which string file to use (9-255). The Element Number sets the string index. The Word Offset sets the word offset within the string (0-41).

File Number

In an Allen Bradley PLC, data is organized as files. The File Number is optional and, if included, sets which file to access. If the File Number is not included the file number is implied by the File Type. All PLC Devices have a predefined set of files as follows:

File	Type
0	Outputs
1	Inputs
2	Status
3	Bit
4	Timer
5	Counter
6	Control
7	Integer

Notes:

On a MicroLogix 1000 PLC no additional files can be defined.
On a MicroLogix 1200 PLC, SLC 5/01 CPU, or SLC 5/02 CPU file 8 is reserved. Additional file numbers 9 to 255 are user defined.
On a other PLC types file 8 is a Float file. Additional file numbers 9 to 255 are user defined.

Element Number

The Element Number sets which element of the file to access.

For Input and Output files, the Element Number indicates which I/O slot to access. An I/O slot may consist of 1 word, or multiple words depending on the type of I/O configured.

For other file types, the Element Number sets which element to access.

Word Offset

The Word Offset field is optional, and if used, defines which word of a multi-word element to access.

Bit Offset

The Bit Offset field is optional, and if used, defines which bit of the word to access.

Data Address Editor

The Data Address Editor provides a convenient tool to build Allen Bradley File Data Address strings.

To open the File Data Address Editor, click on the Browse button at the right side of the DataAddress field:

Variable Reference Format

The Variable Reference Format is used with CompactLogix and ControlLogix PLC Devices.

The Variable Reference Format is a string that defines the location of variable in a tag based Allen Bradley PLC. The format of the string is:

Variable[VarArrayIndexes].StructMember[ArrayIndex]

Allen Bradley Plc Slot Numbering Chart

Where:

Variable is the name of the variable in the PLC.
VarArrayIndexes is an optional set of variable array indexes.
StructMember an optional structure member name.
ArrayIndex is an optional array index on the structure member.

Examples

Some examples of Allen Bradley File Data Addresses:

Address	Description
O:1, O0:1, O:1.0	The first word of output slot 1.
O:1/0, O0:1/0, O:1.0/0	The first bit of the first word of output slot 1.
I:5.1, I1:5.1	The second word of input slot 5
N:20, N7:20	Word 20 of the default integer file
N:20/15, N7:20/15	Bit 15 of word 20 of the default integer file
N10:15	Word 15 of user defined integer file 10

Some examples of Allen Bradley Variable References:

Address	Description
FlowTemperature	A reference to a variable called FlowTemperature.
SCADAData.Pressure	A reference to Pressure member of the variable SCADAData.

Where Used

The Allen Bradley PLC Data Address Format is used in these contexts:

In the IOItemName field of an I/O Analog Data Point Tag when the tag is associated with an Allen Bradley PLC.
In the IOItemName field of a I/O Digital Data Point Tag when the tag is associated with an Allen Bradley PLC.
In the IOItemName field of a I/O Double Word Data Point Tag when the tag is associated with an Allen Bradley PLC.
In the IOItemName field of a I/O String Data Point Tag when the tag is associated with an Allen Bradley PLC.
In the IOItemName field of a I/O Word Data Point Tag when the tag is associated with an Allen Bradley PLC.
In the DataAddress field of an Allen Bradley Register Block.
In the DataAddress parameter of the DirectWriteBit Tag Command when used with an Allen Bradley PLC.
In the DataAddress parameter of the DirectWriteWord Tag Command when used with an Allen Bradley PLC.

Further Information

To learn about Allen Bradley Register Block Tags.

For an overview of the Allen Bradley Driver.

For the meaning of terms used in Fernhill SCADA.