Newbie Here, wondering why it is like this?

Discussion in 'Embedded Systems and Microcontrollers' started by Sakthivvs, Dec 1, 2016.

  1. Sakthivvs

    Thread Starter New Member

    Sep 13, 2014
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    Hello guys,I'm actually new into a forum, I've just stepped into embedded systems, I'm actually confused with Memories,
    I stumbled upon a open source schematic which says 4GB of memory, (MT41J256M16HA-125:E) the datasheet says that density is 4Gb 1.JPG but 4 of such ICs are been used isn't that supposed to be 16Gb's of Memory, wanted to know how this?
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Each chip is only 16 bits wide on its internal address bus.

    It takes 4 to get a 64 bit wide data bus.
     
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  3. Sakthivvs

    Thread Starter New Member

    Sep 13, 2014
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    Well now I get it mate, just correct me if I'm wrong. For a 32bit bus, I'm adding a 8Gb memory of 16bits wide, I Need to place 2 IC's Am I correct?
     
  4. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    4,166
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    No the chip is 4 gig. It's bus width is 16 bits.

    If you stack chips to get a wider bus you still only have 4 gigs.

    Chip 1 is the 16 lowest bits, chip 2 has the next higher place with bits 17 to 31, chip 3 covers bits 32 to 47, and chip 4 has bits 48 to 63.
    Your diagram is to hard to read on this mobile, but look at it closely and note the address lines and then note the numbering on the DATA lines. You will have that light bulb moment any second now.
     
  5. Sakthivvs

    Thread Starter New Member

    Sep 13, 2014
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    Yeah I saw it bro, 2.JPG 3.JPG 4.JPG Well what I'm asking is if I'm gonna place only chip1 and chip2 and leave chip3 and chip4, do I still have 4gigs of memory working in a 32bit bus?
     
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