AVR-Chat

How does the AVR (8515 etc.) access the external RAM, does it start 
from address zero or is the byte @ 0x260 the lowest that can be 
accessed on the chip physically (sounds logical as the internal RAM 
is used below 260h and the address range ends at max. FFFFh)? So only 
way to access the every bit on external RAM is to use max. 32 kB 
(256kbit) RAM and address range 0x8000 -> 0xFFFF? 32 kB chips (62256 
etc. on STK200) don't have A15 so it doesn't matter if it's zero or 
one, right? In fact I'm trying to read and write AT29C256 (which the 
new STK200 can do, don't know how). If anyone has already done this 
it would be nice to borrow his/her wheel.

It looks like that on the STK200 the A15 (of ext. RAM interface = 
port C bit 7) is connected to /CE on 62256 socket (pin 20) so either 
an inverter is needed between the A15 and /CE on RAM socket, or 
the /CE has to be hardwired to GND (which is easier but also a trace 
on the PCB has to be cut). 

--- In AVR-Chat@yahoogroups.com, "mikkohelin" <mikko.helin@l...> 
wrote:
> How does the AVR (8515 etc.) access the external RAM, does it start 
> from address zero or is the byte @ 0x260 the lowest that can be 
> accessed on the chip physically (sounds logical as the internal RAM 
> is used below 260h and the address range ends at max. FFFFh)? So 
only 
> way to access the every bit on external RAM is to use max. 32 kB 
> (256kbit) RAM and address range 0x8000 -> 0xFFFF? 32 kB chips 
(62256 
> etc. on STK200) don't have A15 so it doesn't matter if it's zero or 
> one, right? In fact I'm trying to read and write AT29C256 (which 
the 
> new STK200 can do, don't know how). If anyone has already done this 
> it would be nice to borrow his/her wheel.