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Contents
GFK-0467K vii
Chapter 1 Introduction......................................................................................................... 1-1
Additional Reference Information: See the appendices in the back of this manual....1-2
Chapter 2 System Operation................................................................................................ 2-1
Section 1: PLC Sweep Summary ..................................................................... 2-2
Standard Program Sweep..................................................................................................2-2
Sweep Time Calculation.............................................................................................2-6
Housekeeping.............................................................................................................2-6
Input Scan ..................................................................................................................2-7
Application Program Logic Scan or Solution.............................................................2-8
Output Scan................................................................................................................2-9
Logic Program Checksum Calculation.......................................................................2-9
Programmer Communications Window............................................................................2-9
System Communications Window (Models 331 and Higher) .......................................2-10
PCM Communications with the PLC (Models 331 and Higher)...................................2-12
Standard Program Sweep Variations ..............................................................................2-13
Constant Sweep Time Mode ....................................................................................2-13
PLC Sweep When in STOP Mode ...........................................................................2-13
Communication Window Modes..............................................................................2-14
Key Switch on 350 and 360 Series CPUs: Change Mode and Flash Protect .................2-14
Using the Release 7 and Later Key Switch ..............................................................2-14
Clearing the Fault Table with the Key Switch .........................................................2-14
Enhanced Memory Protect with Release 8 and Later CPUs ....................................2-15
Section 2: Program Organization and User References/Data..................... 2-16
Subroutine Blocks (Series 90-30 PLC only)...................................................................2-16
Examples of Using Subroutine Blocks.....................................................................2-18
How Blocks Are Called............................................................................................2-19
Periodic Subroutines.................................................................................................2-19
User References ..............................................................................................................2-20
Transitions and Overrides...............................................................................................2-21
Retentiveness of Data .....................................................................................................2-21
Data Types ......................................................................................................................2-23
System Status References ...............................................................................................2-24
Function Block Structure ................................................................................................2-26
Format of Ladder Logic Relays................................................................................2-26
Format of Program Function Blocks ........................................................................2-27
Function Block Parameters .............................................................................................2-28
Power Flow In and Out of a Function ......................................................................2-29
Section 3: Power-Up and Power-Down Sequences ...................................... 2-30
Power-Up ........................................................................................................................2-30
Power-Down ...................................................................................................................2-33
Section 4: Clocks and Timers......................................................................... 2-34