Justin Hollis ET2750 Exercise 2.1

1) In Allen-Bradly PLCs memory is organized using either rack-based systems or tag-base systems. 2) The difference is that the newer Logix series PLCs use variable and tag based systems. 3) In the Rack / Slot system the slot locations in the rack determine the location of the I/Os in the system.
In a tag-base system the variable names for the I/Os are defined when there designed. 4) Data files hold memory locations and instructions.
Program files contain the controller information, main ladder program, interrupt subroutines, and all other subroutine programs. 5) Output Image 32 words1
Input Image 32 words1
Status 12 words1
Bit (Binary) 1000 words
Timer 1000 structures (3000 words)2
Counter 1000 structures (3000 words)2
Control 1000 structures (3000 words)2
Integer 1000 words
Floating Point 1000 structures (2000 words)2
ACII 1000 words
BCD 1000 words
Block Transfer 1000 structures (6000 words)2
Message 585 structures (32760 words)2
PID 399 structures (32718 words)2
SFC status 1000 structures (3000 words)2
ASCII string 780 structures (32769 words)2
User Defined 6 6) The data files for a PLC 5 contain an identifier indicated by letters in the file type. Data files for a SLC 500 store a number of instructions or memory locations based on the instructions stored in the file. 7) Project – a collection of all the program elements.
Task – holds the information necessary to schedule the programs execution and sets the priority of execution for multiple programs.
Program – executable task.
Main routine – when a program executes it is the first to call subroutines. Subroutine – any routine other than the main routine. 8) It starts with an I for input or an O for output followed by a colon