Basic Allen-Bradley Micrologic memory organization

U:2

Main Program

U:6 through U:16

User programs / Data

O: word/bit

Output status file – Transfers a signal to field devices

I: word/bit

Input status file – Stores logic signals produced by input devices

B3: word/bit or B3/bit

Binary/Bit file – Internal relay logic instructions

T4: word group. word/bit

Timer file – Timing operations

C5: word/bit

Counter file – Counting operations

R6: word group. word/bit

Control file – Shift registers / Sequencing

N7: word/bit

Integer file – Stores numerical values

List the main components of a programmable controller

1: Chassis/ Back Plane

2: Processor

3: I/O Cards

4: Power Supply

Advantages and disadvantages of using PLC’s

Cons: Upfront cost/ Training

Pros: Simplified Wiring, Simplified Troubleshooting, Automatic Documenting

List four factors that effect the PLC’s scan cycle

Speed of Processor

Complexity

Length of the program

Number of I,O Points