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Retentive Memory

Created by: Saradhi at: 5/29/2012 8:35 AM (6 Replies)

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5/29/2012 8:35 AM	Rate (0)
Saradhi Posts: 303 Rating: (3)	Dear All, In S7-300 i have a program of 50KB and i want to retentive 400 bytes of memory. for this purpose how much capacity of MMC card i preferred. how can i make 400 bytes of memory as retentive.
Saradhi Posts: 303 Rating: (3)
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5/29/2012 9:03 AM	Rate (0)
Darius Platinum Expert Joined: 9/28/2005 Last visit: 8/27/2024 Posts: 2957 Rating: (242)	Saradhi Dear All, In S7-300 i have a program of 50KB and i want to retentive 400 bytes of memory. for this purpose how much capacity of MMC card i preferred. how can i make 400 bytes of memory as retentive. Retentive area is set up in the HW config of the CPU. Can't tell much about MMC capacity, but you can always check blocks properties and you will see how much MMC you need and how much internal memory you need.
	Best regards, Darius
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5/29/2012 9:28 AM	Rate (0)
Ganes10 Platinum Member Joined: 8/31/2010 Last visit: 9/3/2024 Posts: 1520 Rating: (227)	Saradhi Dear All, In S7-300 i have a program of 50KB and i want to retentive 400 bytes of memory. for this purpose how much capacity of MMC card i preferred. how can i make 400 bytes of memory as retentive. Hello Saradhi, You can set the retentivity for Marker (Bit Memory), Timer, Conunter in the HW Config. By default all the Shared DB are retentive, if need be you have to choose Non-Retentive DB option manually in the corresponding DB. Regarding calculating the MMC size, refer this FAQ How can you determine the size of the load memory and main memory of a SIMATIC S7-300/400 CPU? Your MMC is nothing but load memory - so calculate accordingly.
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5/29/2012 9:33 AM	Rate (0)
Saradhi Posts: 303 Rating: (3)	Can you help me regarding MMC card selection
Saradhi Posts: 303 Rating: (3)
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5/29/2012 9:40 AM	Rate (0)
Marko Bursic Platinum Member Joined: 9/8/2009 Last visit: 7/17/2023 Posts: 1410 Rating: (152)	Take a card that has 2 times more capacity than CPU memory has(suggestion only).

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5/29/2012 10:02 AM	Rate (0)
Ganes10 Platinum Member Joined: 8/31/2010 Last visit: 9/3/2024 Posts: 1520 Rating: (227)	[quote user="Marko Bursic"]Take a card that has 2 times more capacity than CPU memory has(suggestion only). Hello Marko, it's not economical in my opinion, it is ok to choose a high capacity card if u have future expansions planned If you have the program ready before procurement, then it's easy to determine the memory requirement as mentioned above
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5/29/2012 10:27 AM	Rate (0)
Darius Platinum Expert Joined: 9/28/2005 Last visit: 8/27/2024 Posts: 2957 Rating: (242)	Saradhi Can you help me regarding MMC card selection If you don't have enough experience selecting memory card you then have several options: 1. Write most part of a program and then check block properties and you will have some idea on final load memory demand. 2. If you company has enough money buy at least 1MB card and send it to plant. Once program is finished, you will see real size of MMC then you buy correct MMC and bring back home that 1MB card which can be your nice test card
	Best regards, Darius
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