GE 90-30/20/Micro Section 6: Series 90-30, 90-20, and Micro I/O System................................. 2-38, Section 2: PLC Fault Table Explanations........................................................3-7

Contents
viii Series 90-30/20/Micro Programmable Controllers Reference Manual–September 1998 GFK-0467K
Elapsed Time Clock........................................................................................................2-34
Time-of-Day Clock......................................................................................................... 2-34
Watchdog Timer .............................................................................................................2-35
Constant Sweep Timer....................................................................................................2-35
Time-Tick Contacts.........................................................................................................2-35
Section 5: System Security................................................................................2-36
Passwords........................................................................................................................2-36
Privilege Level Change Requests ...................................................................................2-37
Locking/Unlocking Subroutines..................................................................................... 2-37
Permanently Locking a Subroutine.......................................................................... 2-37
Section 6: Series 90-30, 90-20, and Micro I/O System................................. 2-38
Model 30 I/O Modules....................................................................................................2-39
I/O Data Formats.............................................................................................................2-41
Default Conditions for Model 30 Output Modules.........................................................2-41
Diagnostic Data...............................................................................................................2-41
Global Data..................................................................................................................... 2-42
Model 20 I/O Modules....................................................................................................2-42
Micro PLCs.....................................................................................................................2-43
Chapter 3 Fault Explanation and Correction.....................................................................3-1
Section 1: Fault Handling.................................................................................. 3-2
Alarm Processor................................................................................................................3-2
Classes of Faults ...............................................................................................................3-2
System Reaction to Faults.................................................................................................3-3
Fault Tables................................................................................................................ 3-3
Fault Action................................................................................................................3-4
Fault References................................................................................................................3-4
Fault Reference Definitions.............................................................................................. 3-5
Additional Fault Effects....................................................................................................3-5
PLC Fault Table Display ..................................................................................................3-5
I/O Fault Table Display.....................................................................................................3-5
Accessing Additional Fault Information...........................................................................3-6
Section 2: PLC Fault Table Explanations........................................................3-7
Fault Actions.....................................................................................................................3-8
Loss of, or Missing, Option Module.......................................................................... 3-8
Reset of, Addition of, or Extra, Option Module.........................................................3-9
System Configuration Mismatch..............................................................................3-10
Option Module Software Failure..............................................................................3-11
Program Block Checksum Failure............................................................................3-11
Low Battery Signal...................................................................................................3-11
Constant Sweep Time Exceeded.............................................................................. 3-12