Memory Layout and Memory Layout and SLC500™ System SLC500™ System

AddressesAddresses

Processor Memory Processor Memory DivisionDivision

• An SLC 500 processor's memory is An SLC 500 processor's memory is divided into two storage areas. Like divided into two storage areas. Like two drawers in a filing cabinet, one two drawers in a filing cabinet, one area is for data files and the other area is for data files and the other for program files. Processor memory for program files. Processor memory division and file capacity are shown division and file capacity are shown in the following graphic:in the following graphic:

Program FilesProgram Files

• Program files contain processor Program files contain processor information, the main ladder information, the main ladder program, and other ladder files. An program, and other ladder files. An SLC 500 processor can contain up to SLC 500 processor can contain up to 256 program files. Program files are 256 program files. Program files are located in the Program Files folder located in the Program Files folder of the RSLogix 500 project tree, as of the RSLogix 500 project tree, as shown in the following graphic:shown in the following graphic:

• Program files are assigned as follows:Program files are assigned as follows:

• File 0 always contains system File 0 always contains system information.information.

• File 1 is reserved.File 1 is reserved.

• File 2 contains the main ladder file.File 2 contains the main ladder file.

• File 3-255 contains other ladder files File 3-255 contains other ladder files (subroutines).(subroutines).

Data FilesData Files

• DataData files contain the status files contain the status information associated with external information associated with external I/O and all other instructions used in I/O and all other instructions used in the main and subroutine ladder the main and subroutine ladder program files. Data files are located program files. Data files are located in the Data Files folder of the in the Data Files folder of the RSLogix 500 project tree, as shown RSLogix 500 project tree, as shown in the following graphic:in the following graphic:

• Data files are assigned as follows:Data files are assigned as follows:• File O0 stores the state of output terminals.File O0 stores the state of output terminals.• File II stores the state of input terminals.File II stores the state of input terminals.• File S2 stores processor operation data.File S2 stores processor operation data.• File B3 stores internal relay logic.File B3 stores internal relay logic.• File T4 stores the timer accumulator and preset values and File T4 stores the timer accumulator and preset values and

status bits.status bits.• File C5 stores the counter accumulator and preset values and File C5 stores the counter accumulator and preset values and

status bits.status bits.• File R6 stores the length, pointer position, and status bits for File R6 stores the length, pointer position, and status bits for

specific instructions such as shift registers.specific instructions such as shift registers.• File N7 stores whole number values, both negative and positive File N7 stores whole number values, both negative and positive

or bit-level information.or bit-level information.• File F8 stores positive and negative numbers that include aFile F8 stores positive and negative numbers that include a

decimal point.decimal point. ,,• Files 9-255 store user-defined data.Files 9-255 store user-defined data.

•SLC 500 Software and SLC 500 Software and Hardware Addressing:Hardware Addressing:

SLC 500 Processor Data SLC 500 Processor Data Storage Units:Storage Units:

• The SLC 500 processor stores data in the following units The SLC 500 processor stores data in the following units of memory:of memory:

• Bit:Bit: A digit in the binary radix (0 or 1). A bit may A digit in the binary radix (0 or 1). A bit may represent the state, on or off, of a discrete I/O device.represent the state, on or off, of a discrete I/O device.

• WordWord: : A sequence of 16 bits that is treated as a unit. For A sequence of 16 bits that is treated as a unit. For example, the 16 bits representing the 16 points of an I/O example, the 16 bits representing the 16 points of an I/O module comprise one word.module comprise one word.

• ElementElement: : A word or group of words that work together as A word or group of words that work together as a unit.a unit.

• Sub-elementSub-element: : Individual words within an element.Individual words within an element.TypeType: : A group of words or elements with a common A group of words or elements with a common usage usage

• FileFile: A consecutive array of words addressable as a unit.: A consecutive array of words addressable as a unit.

SLC 500 Software Address SLC 500 Software Address Characteristics:Characteristics:

• SLC 500 software addresses (internal SLC 500 software addresses (internal storage addresses) are used for processor storage addresses) are used for processor and program control. A software address is and program control. A software address is a value stored within a processor's data file a value stored within a processor's data file that is not directly connected to real-world that is not directly connected to real-world inputs or outputs.inputs or outputs.

• The following SLC 500 software address The following SLC 500 software address format is used for bits stored in status, format is used for bits stored in status, binary, tinier, counter, control, integer and binary, tinier, counter, control, integer and floating point data table files:floating point data table files:

The following SLC 500 software address format is used for The following SLC 500 software address format is used for sub-elements stored in timer, counter, and control files:sub-elements stored in timer, counter, and control files:

SLC 500 Hardware Address SLC 500 Hardware Address Characteristics:Characteristics:

• The address for a real-world device (input or output) is The address for a real-world device (input or output) is directly determined by the module slot number and directly determined by the module slot number and terminal to which the hardware device is wired.terminal to which the hardware device is wired.

• Slot numbers are assigned from left to right, beginning Slot numbers are assigned from left to right, beginning with 0. The SLC 500 processor is in slot 0.with 0. The SLC 500 processor is in slot 0.

• A hardware address contains the following information:A hardware address contains the following information:• The module type, either an input (I) or an output (O) The module type, either an input (I) or an output (O)

modulemodule• The slot number (numbered in decimal from 1 to 30)The slot number (numbered in decimal from 1 to 30)• The terminal number (numbered in decimal from 0 to 15)The terminal number (numbered in decimal from 0 to 15)

An example of an SLC 500 I/O address is shown in the An example of an SLC 500 I/O address is shown in the following graphic:following graphic:

I/O Addresses:I/O Addresses:

• The input and output data tables store the states of The input and output data tables store the states of input and output devices. The two files have the input and output devices. The two files have the following characteristics:following characteristics:

• Each I/O module terminal point is represented by a Each I/O module terminal point is represented by a bit stored in either the input or output data tables.bit stored in either the input or output data tables.

• The bits in the input data table store data from The bits in the input data table store data from input modules; bits in the output data table store input modules; bits in the output data table store data going to the output modules.data going to the output modules.

• If a bit has a value of 1, it means the terminal point If a bit has a value of 1, it means the terminal point it represents is "on." If a bit has a value of 0, it it represents is "on." If a bit has a value of 0, it means the terminal point it represents is "off."means the terminal point it represents is "off."

The following graphic illustrates the relationship between a The following graphic illustrates the relationship between a 16-point input module and the input data table: For modules 16-point input module and the input data table: For modules with more than 16 terminal points, a ".1" is added to the slot with more than 16 terminal points, a ".1" is added to the slot number column of the data table to indicate the row number column of the data table to indicate the row containing terminals 16 and beyond.containing terminals 16 and beyond.

Determine SLC 500 Determine SLC 500 Software Addresses:Software Addresses:

• The following graphic shows an SLC The following graphic shows an SLC 500 software address for the 2nd bit 500 software address for the 2nd bit in the 3rd word in binary file 15. In in the 3rd word in binary file 15. In the example, note the position and the example, note the position and order of the file type, file number, order of the file type, file number, word or element, and bit number:word or element, and bit number:

Determine SLC 500 Determine SLC 500 Hardware Addresses:Hardware Addresses:

• The following graphic shows an SLC The following graphic shows an SLC 500 hardware address for terminal 500 hardware address for terminal number 10 of an input module in slot number 10 of an input module in slot 3. In the example, note the position 3. In the example, note the position and order of the module type, slot and order of the module type, slot number, and terminal number:number, and terminal number: