почитал и решил 000 - наш выбор :)
Introduction
ARM's Advantage memories at 90nm can be run at different voltages with the
same GDS. Extra Margin Adjustment (EMA) pins can be used to enable this
benefit without affecting the performance at the higher voltage. In other
words, instead of super-margining the memory, it is margined at different
voltage ranges with different EMA settings.
It has been found that when EMA is set to a value other than 000 during
power up, the Advantage SP-SRAM and DP-SRAM memory compilers at 90nm don't
always power up to a state that allows correct functionality. This may
manifest itself as a small yield drop-off in non-000 EMA functionality.
This affects all 90nm Advantage SP-SRAM and DP-SRAM compilers. There is a
workaround available to correct this behavior.
Workaround for customers who have hard-coded EMA to a value different from
000
1) All even rows are in the bottom bank and all odd
rows are on the top bank. Accessing both banks would access both even and
odd rows.
2) Perform four read cycles - two to odd (top bank)
and two to even rows (bottom bank)
3) Increment the address by the mux size (8, 16 or
32) in order to access the second row
4) Run four more read cycles - two to odd and two to
even rows
5) After these steps, it is possible to resume
normal active operation of memory
Workaround for customers who have programmable EMA
1) Power-up the memory with EMA set to 000
2) After this step, it is possible to resume normal
active operation of memory
For an example 16Kx16M32 Advantage SP-SRAM instance, all first 32 addresses
(0-31) would make row 0 and (32-63) would make row 1 and (64-95) would make
row 2 and (96-127) would do row 3. Dummy read cycles should access each one
of these addresses like address 0, 32, 64, 128 at EMA=000 and only after
that change it to other EMA settings for normal operation.
Summary
It has been found that the Advantage SP-SRAM and DP-SRAM memory compilers
at 90nm don't always power up to a known state when EMA is set to a non-000
value. There is a workaround available to correct this behavior.