A Clarification about Flash Store on GE IP Controllers
The difference between Download and Flash Write
All programmer operations like Download to Controller, Upload from Controller, Verify or Clear Memory exclusively refer to CPU RAM.
- Information is downloaded from the programmer to CPU RAM or vice-verse.
- Verify compares between programmer and CPU RAM.
All Flash operations like Write, Read and Verify are executed by the CPU and write, read or verify information between CPU RAM and Flash.
- Information is written from CPU RAM to Flash or vice-verse.
- Verify compares between CPU RAM and Flash.
Running the CPU from RAM or Flash
Power up behavior of the CPU is determined through the 'Logic / Configuration From' and 'Registers' parameters in the CPU hardware configuration. Both parameters can be set to RAM, or Flash. Series 90-30 targets call for 'PROM' instead of Flash. However, the option refers to Flash memory. ; *)
Logic / Configuration and Registers are separate parameters, because applications may want to load the Program from Flash, but retain Registers in battery backed RAM.
Note: If Registers are to be loaded from Flash, Logic / Configuration must be set to Flash as well.
- If Logic / Configuration is set to RAM, the CPU powers up with the information from RAM. This setting requires a healthy battery connected to the CPU.
- If set to Flash, the CPU loads information from Flash. This setting does not require a battery, unless Registers are loaded from RAM.
* On PAC Systems CPUs, there exists an additional option of Conditional Flash which is explained further down in this document.
Downloading and storing to Flash
Once configuration and logic are finalized, they are downloaded to the CPU. Like mentioned before, the programming software downloads all selected items to CPU RAM.
There is a download option to 'Store all Items to Flash'. In this case, the programmer still downloads all selected items to RAM and then sends a command to the CPU to write all RAM content to Flash.
Alternatively, Flash operations can be invoked any time from the Flash Menu under Online Commands. (Right click target, select Online Commands, then Flash / EEPROM.)
Flash operations allow the user to write current CPU RAM to Flash or vice-verse and to compare CPU RAM and Flash.
Note: A CPU hardware configuration that is setup to load Logic / Configuration from Flash must be downloaded to the CPU (RAM) and written to Flash. At power up, the CPU first checks its Flash memory. If there is a valid configuration in Flash that is set to load from Flash, then configuration and logic are loaded from Flash into RAM for execution.
Clearing Flash Memory
On PAC Systems, Flash memory can be cleared from the Flash operations dialog. On other GE IP PLCs, the best method to clear Flash is clearing all memory on the CPU (RAM) and then writing (the empty memory) to Flash.
Note: For all Flash operations, the CPU must be in Stop No I/O Mode.
Power Up Source Conditional Flash on PAC Systems CPUs
On PAC Systems CPUs, there exists a third option for power up: Conditional Flash.
If Conditional Flash is selected but there is a valid configuration in RAM, the CPU uses the configuration in RAM.**)
**)Please see the detailed power up conditions for a PAC Systems CPU in the PAC Systems CPU Manual.
GFK-0467 Series 90™-30/20/Micro PLC CPU Instruction Set Reference Manual
GFK-2222 PACSystems* CPU Reference Manual
GFK-1503 VersaMax® PLC User's Manual