Programmable controller backup system

A method of backing up memory data structures from a primary programmable controller system to a secondary programmable controller system using a high speed communications link between backup modules on each of said systems, comprising the steps of:

• on a prioritized basis synchronously crossloading mode change data and program step change data immediately whenever such changes in such data occur;
• delaying program step changes until the crossloading of corresponding step change data is acknowledged by a backup module;
• and
• background crossloading system data tables and files, local processor data tables and files and I/O data tables on one or more periodic bases.

A tightly coupled process for communicating backup information between source client tasks on a primary controller system including a first backup module and destination client tasks on a secondary controller system including a second backup module using a high speed communication link between said modules, comprising the steps of:

• transferring packets of data to be transmitted from source client tasks on modules in said primary system to said secondary system into identified buffer memory locations on said first backup module;
• passing information identifying said packets and their buffer locations to a message transmission object for queuing and processing outgoing packets and interfacing with a communications driver for said link;
• transmitting said packets using said communications driver over said link to buffer memory locations on said second backup module on a prioritized basis;
• passing information identifying said packets and their buffer locations to a message receipt object for queuing incoming packets and interfacing with destination client tasks;
• and
• transferring said packets of data to destination client tasks on modules in said secondary control system.

A method of performing on-line editing of control programs in a programmable controller system including a first processor module and a second processor module used for backup purposes, said method comprising the steps of:

• a) generating a program edit command at a central program object adapted for implementing program edit commands;
• b) generating first and second command check messages at said program object and forwarding these messages to said first and second processor modules for signaling said processors to verify their capabilities for concurrently executing said edit command;
• c) having said processor modules each check their capabilities for executing said edit command in response to said command check messages;
• d) generating first and second command check reply messages at said first and second processor modules for indicating the capabilities of said first and second processor modules to execute said edit command and forwarding these reply messages to said central program object;
• e) halting the further implementation of said edit command at said program object when either of said command check reply messages indicates that the edit command cannot be executed;
• f) generating first and second command do messages at said program object including one or more parts for signaling said processor modules to execute said edit command and forwarding these messages to said first and second processor modules;
• and
• g) having said processor modules execute said edit command in response to said command do messages.