Transferring M580 Hot Standby Projects

Introduction

In an M580 Hot Standby system, both the primary CPU and the standby CPU begin by operating the same application. CCOTF changes that are made to the application running in the primary CPU are not also made to the standby CPU. This causes a logic mismatch to exist between the two CPUs.

After modifications, it is necessary to transfer the application from the primary CPU to the standby CPU, so that both CPUs are once again operating the same application. There are many ways to make this transfer.

NOTE: The operating mode setting of a safety PAC – either safety mode or maintenance mode – is not included in the transfer of an application from the primary PAC to the standby PAC. On a switchover, when a safety PAC switches from standby PAC to primary PAC, the operating mode is automatically set to safety mode.

For additional information on safety CPU operating modes, refer to the Modicon M580 Safety Manual.

Transferring the Application from the Primary CPU to the Standby CPU

The Control Expert application can be transferred from the primary CPU to the standby CPU in many ways, including the following:

Automatic transfer: If the non-primary CPU is in a non-configured state, the primary CPU automatically transfers the application program and data to the non-primary CPU when it powers up. There are several ways a CPU can be put into in a non-configured state, including:
- It is a new device that is being deployed for the first time.
- Its A/B/Clear rotary selector switch was set to “Clear”, powered-up, then re-set to “A” or “B” (depending on the A/B designation of the primary CPU).
  
  NOTE: To place the standby CPU into run mode on restart, set the CMD_RUN_AFTER_TRANSFER DDDT command to true before power-up.
Transfer from PC to the standby CPU: If your PC with Control Expert has open the same application as the one running in the primary CPU, you can transfer the application from your PC to the standby CPU. To do this, connect your PC to either the Ethernet service port or USB port of the standby CPU, then use the PLC → Transfer Project to PLC command to make the transfer.

NOTE: If the standby PAC is connected to a configuration tool, such as Control Expert, only the connected configuration tool can transfer an application to the standby PAC. In this case, the primary PAC cannot transfer an application to the standby.
Transfer from primary CPU to standby CPU: With Control Expert connected to the primary CPU, and with both the primary and standby CPUs running, use one of the following methods to make the transfer:
- Use the Control Expert PLC → Transfer Project from Primary to StandBy PLC GUI command.
  
  or
- Use the CMD_APP_TRANSFER command of the T_M_ECPU_HSBY DDT.
NOTE:
- The application transferred is the backup application, stored in flash memory or on the SD card. If the application running does not match the backup application, perform an application backup (PLC → Project Backup... → Backup Save or set the %S66 system bit to 1) before performing the transfer.
- If the CMD_RUN_AFTER_TRANSFER flag is set, the standby CPU automatically starts to run after completion of the transfer, reducing down time for the standby CPU.
In each case, if both the primary and standby CPUs are equipped with SD memory cards, the application is transferred to both the standby CPU and its SD memory card.
SD memory card: If the primary CPU includes an SD memory card with the current application, take the SD card from the primary CPU, place it into the standby CPU, then reboot the standby.

In each case:

The application is transferred only if the application in the standby CPU is different from the application being transferred to it.
If the application running in the primary CPU is different from the application stored in flash memory or on the SD memory card, perform a backup of the running application (PLC → Project Backup → Backup Save) before making the transfer.

NOTE:

You cannot transfer the application from the standby CPU to the primary CPU.
If the Logic_Mismatch_Allowed command is set, and if the Number of modifications has not been reached, you can connect Control Expert to the standby CPU, then use the CMD_SWAP DDT command to make the standby CPU the primary CPU. Thereafter, you can transfer the application from new primary CPU (formerly the standby) to the standby CPU (formerly the primary).

Run After Transfer

If you use program logic or an animation table to set the T_M_ECPU_HSBY DDT command CMD_RUN_AFTER_TRANSFER, the primary PAC automatically begins to run immediately upon completion of the transfer.