DDR external memory HELP!!

[xtr0d3m0n]

Hi So In the ADR/CMD group in the memory side Theres a pin called A10/AP what is this pin? and it seems like it connect to a different pin in MPU called SDA10? why does it have a different name than normal address line(like A1,A2 etc).Also in JESD79-3E I don't see any lengh matching over view like match this group to this tolerance.may be that not that easy ?? How ever I manage to read a lot of documents and made my self a chart of length matching....Also can somebody please point out main differences between DDR,DDR2,DDR3,DDR4 in a layout perspective. I kinda have an Idea about how to layout things but I cannot distinguish what are the exact difference.I am trying to decipher the "black magic" and I am not that smart so any help would be very appreciated.The schematics I am referencing is this http://hforsten.com/making-embedded-linux-computer.html

[bitslice]

Hi So In the ADR/CMD group in the memory side Theres a pin called A10/AP what is this pin? a

that's the auto precharge pin, part of the refresh system

https://www.micron.com/products/datasheets/%7BF93E3738-B1AB-44AE-B4D7-0CB043145517%7D?page=8


it's connected to sda10 on the microcontroller, which is its inbuilt DDR2 control logic

[nctnico]

With SDRAM and DDRx memory the RD, WR and select signals form a 3 bit command instead of being used individually. The 11th address line serves a dual purpose. This should be explained in the memory's datasheet! If not clear you can download a datasheet from a different manufacturer to see if the explaination is more clear. The basics of SDRAM and DDRx memory are the same.