Hi,
I managed to use the CPU cycle count from PowerTOSSIM to measure the
possible difference.
It seems that ROM is roughly about 50% slower.
Here are the numbers showing the difference in three of my functions. RAM
access was coded with "table[addr]", ROM access was coded with "PRG_RDB()".
Function | RAM cycles | ROM cycles
f1 | 426 | 666
f2 | 1095 | 2039
f3 | 170 | 278
Regards
Artur
2007/5/17, Michael Schippling <[EMAIL PROTECTED]>:
I guess if there's no indication in the manual,
the thing to do would be to compile a couple examples
down to ASM and see if different instructions are used.
As far as I know there are no internal mem access wait-states.
MS
Artur Skrajnowski wrote:
> I am asking because i stumbled upon this:
> tinyos-1.x\tos\lib\TinySec\SkipJackM.nc, lines 74-80
>
> "F-BOX
> It can live in either RAM (faster access) or program memory (save ram,
> but slower access). The type CRYPTO_TABLE_TYPE, defined in crypto.h
> defines where we drop the table and how we access it. This is necessary
> to compile for the PC target since it doesn't support tables in program
> memory the same way.
> static const CRYPTO_TABLE_TYPE SJ_F[] = {...}"
>
> The comment seems to imply that there is a performance difference
> between reads from ROM/RAM but I cant find any other info than this.
>
> Help is welcome
>
> Rgds
> Artur
>
> 2007/5/17, Michael Schippling <[EMAIL PROTECTED]
> <mailto:[EMAIL PROTECTED]>>:
>
> A quick review of the ATMEGA manual reveals...nothing...
> I suspect that access times are the same, for reads anyway,
> on both internal memories because instructions seem to take
> the same number of clock cycles. More manual study would
> be indicated however...
>
> MS
>
> Artur Skrajnowski wrote:
> > Hi,
> >
> > Does anyone know the difference in the ROM and RAM memory access
> times
> > for MICA2 in TinyOS?
> > I have a table lookup heavy app and would like to know how
> performance
> > might change if I placed the table in ROM or RAM.
> > Unfortunately I dont a have a mote to test it "live".
> >
> > Any links to docs / articles touching this subject would also be
> apreciated.
> >
> > Thanks for the help.
> >
> > --
> > Regards
> > Artur Skrajnowski
> >
> >
> >
>
------------------------------------------------------------------------
> >
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> <mailto:[email protected]>
> >
>
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>
>
>
>
> --
> Pozdrawiam
> Artur Skrajnowski
> [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>
--
Pozdrawiam
Artur Skrajnowski
[EMAIL PROTECTED]
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