Skip to Content

Register Login

Industry Online Support

Technical Forum

Navigation

DB size

Created by: jiwan2k at: 8/12/2009 8:54 AM (4 Replies)

Rating (1)

Thanks 1

5 Entries

8/12/2009 8:54 AM	Rate (0)
jiwan2k Member Joined: 7/27/2009 Last visit: 8/17/2009 Posts: 3 Rating: (0)	Hi, I am just studying about the PLC. exactly about DB size. There are something I do not understand. As you can see the PDF file I attached, the upper part of the file, there are 4 kinds of CPU. The DB numberof the first two items(CPU 312, 314) are 511, and the others are 1023. However, the DB sizes are all same, 16Kbytes. here' s thing. the size(16Kbytes)meansone DB size? so, for example, CPU 312's DB total size is 8176Kbytes?. up to now,I don'tunderstand and think likethat. In my opinion,the size(16Kbytes) is the total DB size, so, just one DB size is about 31.3(16000/511) bytes.Am I right? please help me out of this problem. Thanks in advance for you helps. lotsof love. Attachment DB size.pdf (934 Downloads)

Suggestion To thank Quote Answer

8/12/2009 9:14 AM	Rate (0)
RBM Bronze Member Joined: 8/21/2008 Last visit: 8/23/2024 Posts: 141 Rating: (6)	Hi jiwan2k, I think the each DB should have max of 16KB. (I didnt find any supporting document to prove it.) As per your calculation, if CPU 315-2DP has 16KB as max size, then each DB should have only upto 16*1024(KB to Bytes) / 1023 (max number of DB) so each should only have max of 16 bytes. but im using max of 1KB for each DB. Thats why i said each DB should have a max of 16KB. rgds, RBM
	Last edited by: RBM at: 8/12/2009 9:28 AM
Suggestion To thank Quote Answer

8/12/2009 9:49 AM	Rate (0)
jiwan2k Member Joined: 7/27/2009 Last visit: 8/17/2009 Posts: 3 Rating: (0)	Hi, RBM~ Thanks a lot. it's better to understand after your explanation. but I need that topic to be clear. You mean that each DB size could be 16KB. I understood that. sometiems, people use a lot DB or not. So, Max could be 16KB, How about this? is it possible that the whole DB size can be 16368KB(16 * 1023) in case of CPU 315-2 DP? If I know the max of the total DB's size, I will have no problem. :) If anyone knows, let me know. Thanks in advance. lots of love.
	Last edited by: jiwan2k at: 8/12/2009 9:52 AM
Suggestion To thank Quote Answer

8/12/2009 10:41 AM	Rate (1)
Aret Posts: 2348 Rating: (264)	You mix everything togherther :^) There 3 absolutely different restrictions on CPU 1) Number of Dbs. 511 and 1023 in your case. It means you cant have DB2000 even though it would be the only DB in your project. 2) DB size. Each DB can be 16Kb. But see restiction 3 3) Work memory size of CPU. CPU has total number of bytes it can assign to DB area in work memory, so sum of your Dbs shouldn't exceed that number. PS. There is also load memory limitation, but it can be regulated with MMC of bigger size. Work memory CANT be extended.
Aret Posts: 2348 Rating: (264)
Suggestion To thank Quote Answer
This contribution was helpful to 1 thankful Users RBM

8/17/2009 7:08 AM	Rate (0)
jiwan2k Member Joined: 7/27/2009 Last visit: 8/17/2009 Posts: 3 Rating: (0)	Hi, Aret~! Thanks for everything, now i can understand what you're saying. hav a fabulous day~!

Suggestion To thank Quote Answer

|

Share this page:

Share this page on...

Follow us on