GE 90-70 Scan Synchronization

4-6 Series 90™-70 Enhanced Hot Standby CPU Redundancy User's Guide – May 2000 GFK-1527A

4

Scan Synchronization

The figure below shows the sweep comp on ents for the active and the backu p C PUs.

1

ACTIVE CPU

Housekee

p

in

g

In

p

ut Scan

Send In

p

uts

and

S

y

nchronize

Lo

g

ic Solution

Send Out

p

uts

and

Other Data

Out

p

ut Scan

Windows

and

Run-Time Dia

g

nostics

BACKUP CPU

Housekee

p

in

g

In

p

ut Scan

Receive In

p

uts

and

S

y

nchronize

Lo

g

ic Solution

Receive Out

p

uts

and

Other Data

Out

p

ut Scan

Windows

and

Run-Time Dia

g

nostics

DATA

DATA

2

1

2First Data Transfer Occurs: %I, %AI

Second Data Transfer O ccurs: %Q

,

%AQ

,

%R

,

%M

There are two communication poin ts in the sweep. The first communication point is immediately

after the inputs are scanned. At this point in the sweep the newly-read inputs are sent from the

active CPU to the backup CPU and synchronization information is passed. In the second

communication point, the rest of the data (outputs, internal references, registers) is sent from the

active PLC to the backup. These data transfers are automatic; they require no application program

logic (but do require proper configuration).

Data can be transferred on either Redundancy Communications Module link. If one link fails, the

transfer switches to the other link without causing a loss of synchronization.

Input Data and Synchronization Data Transfer to the Backup Unit

Immediately after the Input Scan, the active unit sends the selected input data (%I, %AI) to the

backup unit. For discrete data, the status, override, and transition information is transferred. If

point faults are configured, point fault data is also sent.

The data is transferred in blocks. Each block is checked for data int egr ity. The backup CPU holds

the transferred data in a temp orar y area until all the data has been recei ved a nd verified. Then the

backup CPU copies the data into the actual PLC memories. If the full transfer fails to complete

properly, the backup unit disregards the data in the temporary area and instead uses the values it

obtained during its own input scan.

Sweep Time Synchronization

During the first transfer, the active unit automatically sends a synchronizing message to the backup

unit. This message contains the Start of Sweep Time. The CPUs stay synchronized because the

active unit waits for the backup CPU to respond to the synchronizing message before starting its

sweep.

Contents

Main Warnings, Cautions, and Notes as Used in this Publication Warning Caution Note Preface Content of This Manual Related Publications Preface Contents Page Page Page Introduction Definition of Terms Enhanced Hot Standby CPU Redundancy Features of Enhanced Hot Standby CPU Redundancy Using the Redundancy CPU for Non-Redundant Op eration Compatibility with CPU780 Redundancy CPUs as Compared to Other Series 90-70 CPUs Features not Available with Redundancy CPUs Differences in Operation for Redundancy CPU s Components of the Enhanced Hot Standby Redundancy System Enhanced Redundancy CPU Module Redundancy Communications Module Redundant Racks I/O Systems for Enhanced Hot Standby CPU R edundancy Genius I/O Local I/O Cable Connections GFK-1527A Chapter 1 Introduction 1-7 Enhanced Hot Standby CPU Redundancy Syst em with Local I/O TERMINATED I/O CABLE --- * Secondary Unit Primary Unit Control Strategies GHS Control Strategy GDB Control Strategy Basic Enhanced Hot Standby Operation Output Control with GHS Output Control with GDB Basic CPU Redundancy Setups Single Bus with Prefer red Master: GHS Contro l Strategy Single Bus with Floating Master: GDB Control Strategy Dual Bus with Floating Master: GDB Control Strategy Duplex CPU Redundancy Online Programming On-Line Repair System Components For Installation Instru ctions System Racks Redundancy CPU Features CPU Architecture Expansion Memory Board Watchdog Timer CPU Features Memory Protect Keyswitch CPU LEDs OK: The OK LED is ON when the CPU is functioning properly. The RUN: This LED is ON when the CPU is in the RUN/ENABLE or RUN/DISABLE mode. It is CPU Mode Switch Run/Outputs Enabled Mode Run/Outputs Disabled Mode Stop Mode Port 1 Redundancy Communications Module Unit Select Pushbutton Connector RCM Status LEDS Board OK: Local System Ready Local System Active Bus Transmitter Module Bus Transmitter Module S tatus LEDs Bus Receiver Module Cables and Termination Bus Receiver Module St atus LEDs Board OK: The top LED is ON when the CPU completes its power-up configuration of Last Rack: The middle LED is ON when the terminator plug is installed in the bottom Genius Bus Controller Location of GBCs and Blocks Single Bus Genius Networks Dual Bus Genius Networks Bus Controller LEDs Module OK: The top LED is ON when the board has CH 1 OK: The CH 1 OK LED is ON after the board has Configuration Requirements Programmer Connection for Configuration One Application Program in Both PLCs Program Folders in Control Programming Software Program Folders in Logic master 90 CPU Configuration Parameters Configuring Shared I/O References Finding the Memory Available for Application Program Storage System Communications Win d ow Con siderations Configuring the Redundancy CPU for Non-redundant Operation Rack Module Configuration Parameters Bus Controller Configuration Parameters Genius I/O Block Configuration Parameters Normal Operation Powerup of a Redundant CPU Incompatible Configurations Resynchronization of a Redundant CPU GHS Control Strategy GDB Control Strategy %S References for CPU Redundancy OVR_PRE %S Reference Not Available Scan Synchronization Input Data and Synchronization Data Transfer to the Backup Unit Sweep Time Synchronization GFK-1527A Chapter 4 Normal Operation 4-7 Output Data Transfer to the Backup Unit DATA DATA Data Transfer Time Fail Wait Time Page Programming a Data Transfer from Backup Unit to Active Unit Data Transfer Example Disabling Data Transfer Copy in Backup Unit (SVCREQ #43) Warning Command Block for SVCREQ #43 Backup Qualification w ith SVCREQ #43 Validating the Backup PL C's Input Scan Validating the Backup PLC's Logic Solution Switching Control to the Backup Unit Switching Times Commanding a Role Switch from the Appli cation Program (SVCREQ #26) RUN Disabled Mode RUN Disabled Mode for GHS Control Strategy Example 1: Role switches allowed on both unit s 4-16 Series 90-70 Enhanced Hot Standby CPU Redundancy User's Guide May 2000 GFK-1527A Example 2: Role switches allowed on both unit s The Secondary unit drives the out puts in this example. Example 3: Role switches not a llowed on either unit Example 4: Role switches allowed on both unit s Example 5: Role switches allowed on both units Seco ndary Unit Active Example 6: Role switches not a llowed on either unit, Secondar y Unit Active Example 7: Role switches allowed on both unit s, Secondary Unit Active Example 8: Invalid RUN Disabled Mode for GDB Control Strategy Background User Checksum and Background Window Timing Instructions Finding the Words to Checksum Each Sweep Finding the Background Window Time Finding the Total Sweep Time Miscellaneous Operation Information Timer and PID Function Blocks Timed Contacts Multiple I/O Scan Sets C Debugger STOP to RUN Mode Transition Background Window Time Sequential Function Chart Programming (SFC) Genius Bus Controller Switching Ethernet Global Data in a Redundancy CPU Ethernet Global Data Consumption Ethernet Global Data Production SNTP Timestamping Fault Detection Configuration of Fault Actions Fault Detection PLC Fault Table Messages for Redundancy Page Fault Response Faulting RCMs, Losing Links, a nd Terminating Communications Faulting the Redundancy Communications Modu le Losing a Link Fault Actions in a CPU Redundancy System Configurable Faults * GFK-1527A Chapter 5 Fault Detection 5-9 Non-Configurable Fault Group The table below shows the non-configurable faults and their fault action defaults. Fault Actions Fault Group Table Type Description Not Synchronized Synchronized Fatal Faults on Both Units in the Same Sweep On-Line Repair Maintaining Parallel Bus Termi nation On-Line Repair Recommendation s Power Supply Caution Racks Central Processor Unit Redundancy Communications Module and Cables Redundancy Communications Link Failures Bus Transmitter Module Genius Bus Controller Genius Bus Single Bus Networks Bus faults Dual Bus Networks Genius Blocks Cabling Information Appendix A IC690CBL714A Multi-drop Cable Purpose Specifications A Figure A-1. Multi-Drop Cable Connection Diagram Page Index % A B C E F G H I N O P R S T U V W