Electronic – the data register address for GPIO pin 21 Cortex ARM M0

To answer your base question, to get to the address of pin A10 of the memory you need to look at the memory map for the ARM device...

In this case it looking at the memory map:

0x8000 0000 -> 0x8FFF FFFF is mapped to CSD0 (SDRAM/DDR)

and

0x9000 0000 -> 0x9FFF FFFF is mapped to CSD1 (SDRAM/DDR)

You'd need to know what chip select was used in the PCB design to determine your answer as to which bank your DDR is attached to.

This implies that A10 is located as either 0x8000 0400 (as you mentioned) or 0x9000 0400.

As to why 0x8000 0F00 was used in place of 0x8000 0400...reading the datasheet for that memory implies, but does not state that the other address pins, A(n) are don't cares for this operation so the coder probably just tossed in an F there instead of figuring out that it was only a 4 that was needed.

I also don't find those 2 sections of the datasheet to contradict each other. The first is basically just saying that you need to reference the device's memory map to locate the real address where the memory is mapped so you can use that address as a base.

The second quotes tells you that bit 0 of the address corresponds to address pin 0 on the memory in this mode, which may not always be the case in normal operation. It may depend on the data/address width of the memory combined with alignment issues for the core.

The pins VREFSD+ and VREFSD- are meant to provide an external voltage reference to the Sigma-Delta ADC. This voltage, along with the SDADC bit's resolution, gives you the overall voltage resolution of the converter. This way, the voltage resolution of an ADC is equal to the voltage reference (Vref) divided by 2 to the number of bits of the converter (16 bits in this case), following:

Q = Vref/(2^16)

where: Vref = (VREFSD+) - (VREFSD-), and Q = voltage resolution.

Then, this voltage resolution is the minimum change in voltage that the SDADC will measure. If you connect your device as depicted in your diagram (VREFSD- is usually grounded), the voltage resolution of your SDADC will be:

Q = 3.3[V]-0[V]/(2^16) = 50.35 [uV], approximately.

This means that your system should be able to read a minimum of ~50[uV] (provided correct shielding for noise isolation), and discrete multiples of this value (100[uV],150[uV],...), all to the maximum 3.3[V] of the VREFSD+ pin.

Additionally, you might configure your SDADC (by software) to use these external pins, an internal 1.1/1.8[V] reference or the SDADC power supply as voltage references. If you don't want to use the internal references (which should be extremely accurate), I suggest you to use an external voltage reference circuit to provide a stable voltage and ensure accurate measurements.