Quarterback

Hello guys, I m using s7 400 and flash memory card. as an example we have fc 10 and db 20 . if I update the blocks and function and download the plc. updated blocks will be in ram load memory . which blocks will be used on plc ? priority is ram or memory card? and secondly when we update the data block values and power off plc ( ı have batteries for ram) and power on , plc continue where it left off or not? thank you

 Hello Quarterback;

You are thinking of the priority of the idifferent kinds of load mempry on a S7-400.

Maybe thiss extract can help you:

https://support.industry.siemens.com/cs/ww/en/view/7302549

Load memory:

The load memory can be divided into the external and the internal load memories. The internal load memory is a RAM memory which is integrated into the CPU. Blocks can be transferred from the programming device (PG) to the load memory in the CPU with "PLC/Load". The main memory is updated here at the same time, whereby the runtime-relevant code and data blocks are transferred to the main memory.

The load memory can be extended via a RAM memory card or a flash memory card. The memory card then acts as the external load memory.

If you have a flash memory card plugged in, transfer blocks to the external load memory with "PLC >Load user program onto memory card". However, in the case of "PLC >Load user program onto memory card", the CPU has to be set to STOP mode first before the user program can be transferred.

If you have a RAM memory card inserted, the program can be transferred to the CPU via "PLC > Load". The main memory is also updated here at the same time, whereby the runtime-relevant code and data blocks are transferred to the main memory. The internal RAM load memory is filled first. The other blocks are only written to the RAM memory card when it is full.

All the program blocks and data blocks can be loaded into the load memory via the programming device (PG).

Program blocks will be downloaded to the internal RAM or external RAM card with a Step 7 download command. The PLC's work memory has direct and continuous access to the load memory in RAM. As long as the batteries are able to power the RAM chips/card the program and data are maintained in RAM and accessible upon restart of the PLC.

To load a program in a Flasjh EPROM crd, you need to place the CPU in stop mode, and use the function "Load user program on memory card"; this is a very deliberate act on the programmer's part. And the contents of the Flash EPROM will be transfered to work memory upon restart of the CPU, when there is no battery power to sustain the RAM memory chips.

Hope this helps,

Daniel Chartier