[U-Boot-Users] Where in u-boot is the RAM "Mode Register" programmed?

Bjook bjooky at gmail.com
Thu Mar 22 22:56:01 CET 2007


My question is: Where in u-boot is the RAM "Mode Register" programmed?
Also, is my PCB usable with its mangled RAM address lines?


I am using the "at91rm9200dk" configuration with a couple of changes.  

I ran into problems with the RAM.  We are using a 64Mbit MT48LC2M32 instead
of the 128Mbit MT48LC8M32 which should not be a problem.  Same chip except
for half the capacity.

The only problem is my hardware layout guy decided to mangle the address
lines when he connected the RAM to the ARM processor.  His reasoning was
that a RAM address is a RAM address is a RAM address.  If you always access
the RAM from the Arm chip then the mangled lines will always get decoded and
you will get the correct data value.


What the layout guy did not realize was that this RAM has a Mode Register
that needs to be programmed.  Where does this happen in u-boot?  If I can
find out where it is set then I can decode the mangled address lines and put
the proper value in.

Also I will set the "burst read" to 0.



Do you think this situation salvageable?  A10 is the same because it is a
special line but I may need to jumper A8 and A9 since it looks like they are
only used to program the address register.


The mangled lines are as follows

Normal -> Mangled

A0 -> A1

A1 -> A3

A2 -> A2

A3 -> A11

A4 -> A7

A5 -> A8

A6 -> A6

A7 -> A4

A8 -> A9

A9 -> A0

A10 -> A10


Next time I will fix the mangled lines but I really need to prove out my
design on my current 50 boards since another spin takes around a month
(because of BGA chips).




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