File Structure and Addressing Format of PLC

Introduction

The SLC 500 based system can be configured with or without rack system. The SLC500/PLC-5 can be configure on various sizes of rack system with different number slots. 

The micrologix 1000 and micrologix 1200 based PLC system are shown in figure. In these PLC's there is no need of rack system where Input and output are present at slot 0 for configuration.

      The SLC 500 based system user memory is comprised of data files an program files. The data file 3 through 8 are the default values. Files 9 to 255 can be configure to be bit timer, counter , control, integer , floating point, ASCII , or string files.

Output and Input data files 

The data files 0 or 1 represent external Output and Input , respectively. Table Explain the Addressing Format for Output and input.  The format specifies  e as the slot number and s as word number.

Example:- SLC 5/03 I/O addressing

1. O:2/5 means digital Output of 5 slot 2.
2. O:2 means digital output word 0 of slot 2.
3. I:1/6 means digital input 6 of slot 1.

Status File 

The addresing format of individual bit and complete word in status file. User cannot alter the Status file. To be more precised no addition or deletion is possible in content of status file.

Example:-

S:1/15 means element 1 bit 15. This is the first pass bit which can be used to initiate instruction in program.

Bit Data File 

The default representation of bit file is B3: where any file between the 9 to 255 can be made as bit file if required. The addressing format of individual bit and complete word shown. These file is used the bit instructions, shifht registers and sequencers. The maximum the size of the file is 256 one-word element with a total of 4046 bits. These bit can be used by specifying the element number i.e., 0 to 255 and the bit number i.e. , 0 to 15 within the elements. These bits can also be specifies by numbering them in sequence from 0 to 4095.

Example :-

1. B3:6/15 means bit 12 of element 6.

2. B3:254/6 means bit 6 of element 254.

Timer Data File 

The default representation of timer file is T4: where's  any file between 9 to 255 can be made as timer file if required. The addresing format of individual bit and complete word in timer file is already explained.

        Timer instruction used three control bits. Each data file is made of 3 words data file element. Word 0 is the status word , Word 1 indicate the present Value, and Word 2 indicate the accumulator Value.

Example:-

1. T4:0/15 or T4:0/EN means Enable bit.

2. T4:0/14 or T4:0/TT means timer timing bit.

3. T4:0/13 or T4:0/DN means done bit.

4. T4:0.1 or T4:0.PRE means present Word.

Counter Data File Element

The default representation of counter file is C5 : whereas any file between 9 to 255 can be made as counter file of required. The addresing format of individual bit and complete word in counter file . Each counter address is made of a 3 - word data element. Word 0 is the status word, Word 1 indicate the present value and Word 2 indicate accumulator Value.

Example:-

1. C4:0/15  means counter up bit.

2. C4:0/14 means counter down bit.

3. C4:0/13 means done bit.

4. C4:0/12 means overflow bit.

5. C4:0/11 means underflow  bit.

Control Data File 

The The default representation of counter file is C5 : whereas any file between 9 to 255 can be made as counter file of required. The addresing format of individual bit and complete word in counter file . Each counter address is made of a 3 - word data element. Word 0 is the status word, Word 1 indicate the present value and Word 2 indicate accumulator Value.

Example:-

1. R6:3/15  means enable bit.

2. R6:3/14 means unload Enable bit.

3. R6:3/13 means done bit.

4.R6:3/12 means stack empty bit.

5. R6:3/11 means error  bit.

Integer Data File

The The default representation of integer file is N5 : whereas any file between 9 to 255 can be made as integer file of required. The addresing format of individual bit and complete word in counter file . 

Example:-

1. N7:3/15  means bit 15 of element 3.

2. N7:3 means element 3 of integer 7.

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