Memory Layout and SLC500™ System Addresses

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

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

Program files are assigned as follows: Program files are assigned as follows: File 0 always contains system information. File 0 always contains system information. File 1 is reserved. File 1 is reserved. File 2 contains the main ladder file. File 2 contains the main ladder file. File contains other ladder files (subroutines). File contains other ladder files (subroutines).

Data Files Data files contain the status information associated with external I/O and all other instructions used in the main and subroutine ladder program files. Data files are located in the Data Files folder of the RSLogix 500 project tree, as shown in the following graphic: Data files contain the status information associated with external I/O and all other instructions used in the main and subroutine ladder program files. Data files are located in the Data Files folder of the RSLogix 500 project tree, as shown 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 status bits. File T4 stores the timer accumulator and preset values and status bits. File C5 stores the counter accumulator and preset values and status bits. File C5 stores the counter accumulator and preset values and status bits. File R6 stores the length, pointer position, and status bits for specific instructions such as shift registers. File R6 stores the length, pointer position, and status bits for specific instructions such as shift registers. File N7 stores whole number values, both negative and positive or bit-level information. File N7 stores whole number values, both negative and positive or bit-level information. File F8 stores positive and negative numbers that include a decimal point., File F8 stores positive and negative numbers that include a decimal point., Files store user-defined data. Files store user-defined data.

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

SLC 500 Processor Data Storage Units: The SLC 500 processor stores data in the following units of memory: The SLC 500 processor stores data in the following units of memory: Bit: A digit in the binary radix (0 or 1). A bit may represent the state, on or off, of a discrete I/O device. Bit: A digit in the binary radix (0 or 1). A bit may represent the state, on or off, of a discrete I/O device. Word: A sequence of 16 bits that is treated as a unit. For example, the 16 bits representing the 16 points of an I/O module comprise one word. Word: A sequence of 16 bits that is treated as a unit. For example, the 16 bits representing the 16 points of an I/O module comprise one word. Element: A word or group of words that work together as a unit. Element: A word or group of words that work together as a unit. Sub-element: Individual words within an element. Type: A group of words or elements with a common usage Sub-element: Individual words within an element. Type: A group of words or elements with a common usage File: A consecutive array of words addressable as a unit. File: A consecutive array of words addressable as a unit.

SLC 500 Software Address Characteristics: SLC 500 software addresses (internal storage addresses) are used for processor and program control. A software address is a value stored within a processor's data file that is not directly connected to real-world inputs or outputs. SLC 500 software addresses (internal storage addresses) are used for processor and program control. A software address is a value stored within a processor's data file that is not directly connected to real-world inputs or outputs. The following SLC 500 software address format is used for bits stored in status, binary, tinier, counter, control, integer and floating point data table files: The following SLC 500 software address format is used for bits stored in status, binary, tinier, counter, control, integer and floating point data table files:

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

SLC 500 Hardware Address Characteristics: The address for a real-world device (input or output) is directly determined by the module slot number and terminal to which the hardware device is wired. The address for a real-world device (input or output) is directly determined by the module slot number and terminal to which the hardware device is wired. Slot numbers are assigned from left to right, beginning with 0. The SLC 500 processor is in slot 0. Slot numbers are assigned from left to right, beginning 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) module The module type, either an input (I) or an output (O) module 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 following graphic:

I/O Addresses: The input and output data tables store the states of input and output devices. The two files have the following characteristics: The input and output data tables store the states of input and output devices. The two files have the following characteristics: Each I/O module terminal point is represented by a bit stored in either the input or output data tables. Each I/O module terminal point is represented by a bit stored in either the input or output data tables. The bits in the input data table store data from input modules; bits in the output data table store data going to the output modules. The bits in the input data table store data from input modules; bits in the output data table store data going to the output modules. 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 means the terminal point it represents is "off." 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 means the terminal point it represents is "off."

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

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

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