Chapter 5

Question 1

two different ways of memory structures for ladder logic

Answer 1

• rack based system (address)

- tag based system

Question 2

tag

Answer 2

user friendly name for a memory location, no fixed address

Question 3

first pass bit/status bit

Answer 3

first bit that makes once when go into run mode and then it turns off

Question 4

memory space can be divided into two types of files

Answer 4

• program files: part of processor memory that stores user ladder logic
• data files: store info needed to carry out user program

Question 5

program files

Answer 5

• system functions (0): contains system related info
• reserved (1): reserved by processor
• main ladder (2): ladder logic
• subroutine ladder (3-255): created by user

Question 6

data files

Answer 6

• output (0): output terminals
• input (1): input terminals
• status (2): controller operation info
• bit (3): internal relay logic storage
• timer (4): timer info
• counter (5): counter info
• control (6): stores length, pointer position, and status bit for special instructions
• integer (7): whole numbers
• float (8): fractional data

Question 7

scans

Answer 7

scans from left to right (horizontal)

Question 8

logical continuity

Answer 8

for a output to make or become true, there must be a continuous path of true conditional instructions

Question 9

length of scan depends on:

Answer 9

• speed of processor module
• length of ladder program
• type of instructions executed
• actual ladder true/false conditions

Question 10

plc programming language types

Answer 10

• textural language (instruction list, structured text)

- graphical language (ladder diagram, functional block diagram, sequential function chart)

Question 11

scan process

Answer 11

• read input module
• solve ladder program
• transfer to output module

Question 12

three fundamental symbols for ladder logic

Answer 12

• examine if closed (N.O. contact)
• examine if open (N.C. contact)
• output energize (relay coil)

Question 13

limitations to ladder logic

Answer 13

• can not have a branch within another branch
• no vertical contacts
• there must be logic continuity from left to right only

Question 14

file for storage and addressing of internal output bits

Answer 14

B3