external RAM

[denis_sandrine]

Posted on July 07, 2003 at 06:33

external RAM

[denis_sandrine]

Posted on July 02, 2003 at 11:41

Hi!

I'm working with the ST10f168. I'd like to know how I can use an external RAM with it. I 've looked for this in the datasheet but I haven't found anything yet.

Can you help me?

[maxime2399]

Posted on July 02, 2003 at 14:55

In order to use an external RAM, you need to use the EBC (external Bus Controler).

You need to chose one (or more) chip select (depending on the number of actual RAM device you plan to use)

For each chip select, you need to setup the bus configuration according to the type of bus of the RAM device ( 8-bit or 16-bit, mutiplexed or not, ready signal BHE, wait states...) and to the memory address range you want to use.

Each chip select has its own configuration registers (SYSCON, BUSCONx, ADDRSELx)

The datasheet is not sufficient for the design of your application, you need to have also the user's manual.

Ther is no user's manual for the ST10F168, but you can use the one for the ST10R167 that is fully compatible.

http://www.stmcu.com/mcdfiles/7pdf

You may want to have a look at the ST10F269 instead of the ST10F

It is available today, has few more features and is a little less expensive than the ST10F168 (because it uses a smaller technology)

[ This message was edited by: Max on 02-07-2003 18:27 ]

[denis_sandrine]

Posted on July 03, 2003 at 04:41

Merci bcp pour ta reponse!

En fait, je suis en stage dans une boite depuis 2 jours et ils m'ont demandé de trouver comment ajouter de la RAM externe et quel type de RAM utiliser. Je galère !!!!

Je vais essayer d'avancer un peu grace à ta réponse. Tu peux m'en dire plus sur les Chip Select ??? Tu sais ou je pourrai trouver des exemples parlants????

[ Ce message a ete modifié par : : sandrine82 on 03-07-2003 08:50 ]

[maxime2399]

Posted on July 03, 2003 at 06:41

excuse me if I answer in english, for anybody to understand my answer.

The ST10 can use a huge varitety of external memory: I recomend that you choose your memory according to your application, and then to figure out how to connect it.

try to understand what is the most important in your application:

- the number of i/o available on your ST10:

in multiplexed data and address share the same i/o

8-bit o 16-bit is the possible size of your data bus

the address bus size depend on the memory size

- do you need memory accesses to be very fast or you don't care

demultiplex 16-bit is faster, multiplex 8-bit is the slower

- take in consideration the price of the memory too

faster memory are usually more expensive

16-bit are usually more expensive

Once you have chosen your memory you need to configure the ST10 to access it. Chose a bus type identical to the one of your memory and tune the details parameter (wait state, BHE...) to fit the RAM specification.