Hello sukhoi;

To give you a definite answer, you would need to rovide us with the part number of the CPU you want to work with, because the answer will depend on the genration of CPU you have.

The earliest S7-300s came with integrated, non-expandable load and work memory RAM and EPROM banks, the RAM requiring battery support. Later came CPUs with MC cards, either RAM (with battery support) or Flash EPROM as load memry. The latest generation will use a MMC card as load memry (Flash EPROM).

Here is a document that you can study to find out which generation corresponds to your CPU, in the different tables at the end of the article.

• How can you obtain an overview of the memory concept of SIMATIC S7-300 CPUs and C7 devices?
• https://support.industry.siemens.com/cs/ca/en/view/7302326

The screenshot below will show one of the tables with part numbers from the earliest CPUs of the S7-300 family and their type of memory storage.

Hope this helps,

Daniel Chartier

Hello sukhoi;

This manual dates from 2001, and contains technical information on your CPU; you cannot locate it on SIOS anymore.

https://cache.industry.siemens.com/dl/files/591/8860591/att_105766/v1/HB_CPU312IFM_bis_318-2DP_e.pdf

Data for your CPU 315-2DP )6ES7315-2AF03-0AB0) is shown in the attached screenshot.

As you can see, it shows both integrated work memory, 64 kB RAM, and integrated load memory, 96 kB RAM The ratio should be 1.5 times the load memory to the work memory of the CPU, so this will allow you to download a small program o the CPU, without an additional MC card. If the CPU is in good working state after all these years.

Note that you will require battery suooirt (with a charged battery in the CPU, the battery is designed with a 1-year limited lifesoan)  to maintain the program and data when you shutdown the PLC. The part number is 6ES7971-1AA00-0AA0  this is the link to the datasheet:

https://support.industry.siemens.com/cs/ca/en/pv/6ES7971-1AA00-0AA0/td?dl=en

Hope this helps

Daniel Chartier

Hi,

for your main question - yes you can use it without flash memory because this PLC has integrated work memory and also integrated load memory and load memory is also expandable.

The advantage of a flash EPROM MC is, that you can save programm without puffer batterie.

Technical data

Regards,

Towome