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PIC
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2012/03/15 04:03:41 (permalink)
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Device memory range

Hi, I am using a 24xx102x device (link below). Regarding the memory boundaries, the datasheet says This device has an internal addressing boundary limitation that is divided into two segments of 512K bits. Block select bit ‘B0’ is used to control access to each segment. By "512K bits", is this actually referring to address FA00 (6400), or is it FFFF (65535)? I assume the same goes for the device memory - the datasheet says 1024Kbit, but does that mean 131071bits (1FFFF)? Regarding reading data bytes from the device, the datasheet says After the word address is sent, the master generates a Start condition following the acknowledge. This looks like a Repeated Start, but it just says "Start". Which one is it? Thanks. Link: http://www.microchip.com/...aspx?dDocName=en552658
post edited by PIC - 2012/03/15 04:05:12

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gatorjet
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Re:Device memory range 2012/03/15 06:17:56 (permalink) ☄ Helpful
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I'm trying to understand why the various descriptions keep talking about xxx bits of storage in a device that can only handle bytes.  All it does is muddy the waters.  I would think ignoring the bit referances when discussing the size of the device and talking strictly in terms of bytes would greatly simplify understanding the device.  After all, you can only access it a byte at a time, not by bits.  Just think of this device as having two 64K blocks of memory, the first is at addresses 00000 to 0FFFF and the second 10000 to 1FFFF with the most significant bit of the address residing in B0.
The way I understand a Repeated Start is that it is a mechanism by which the Master switches from a Write to a Read operation without using a Stop in between in order not to relinquish the bus.  A "normal" Start occurs after a Stop condition, whereas a "Repeated Start" does not have a prior Stop condition.  One of its main uses is during a Random Read operation where the Master has to first Write the address to the device and then Read the data from the device. On the bus Start and Repeated Start are both the same, SDA transitioning low while SCL remains high.
 
Hope this helps,
 
Hal
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DarioG
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Re:Device memory range 2012/03/16 03:13:44 (permalink) ☄ Helpful
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1024 Kbits are 128KBytes, yep Smile

And yes, it's a Restart that in the end is a Start without a Stop.

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PIC
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Re:Device memory range 2012/03/21 04:53:27 (permalink)
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Thanks. Just to clarify, "64K" means FFFF as oppose to FA00?

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DarioG
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Re:Device memory range 2012/03/21 07:17:51 (permalink) ☄ Helpful
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hmm, yes, FFFF is 65535... what do you mean exactly?

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PIC
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Re:Device memory range 2012/03/22 03:11:44 (permalink)
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Hi, Just checking that the datasheet doesn't literally mean 64000 when it says "64K" - instead it actually means 65535 (thus FFFF as oppose to FA00).

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DarioG
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Re:Device memory range 2012/03/22 12:06:34 (permalink) ☄ Helpful
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Ah ok!

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