Adding RAM for 89S51/52 ?

Hai,
I want to add some 1K or 2k RAM to my 89S51 project.
Is it too complicated ?
Which is the cheep and freely available part for my purpose?
I have no prior experience in XRAM usage.
I am using keil.

Picstudent

In keil
XRAM Usage:
- methode 1: (Keil version >3.4)
<xdata >+ <unsigned char,int>+<variable_name> + <_at_> + <Addr>
example:
xdata unsigned char abc _at_ 0xF000;
Access variable is normal.
- methode 2: (alls of Keil version)
+ include<intrins.h>
declare: unsigned char abc=5;
read: abc = XBYTE[0xF000];
write: XBYTE[0xF000] = abc;

The 8051 microcontrollers are basically all the same they have a multiplexed address/data BUS ..in order to connect external devices mapped to this space is required a register (74LS373) in order to latch the the lower addresses .For such a small requirement 2k or 4k there are plenty of other 51 derivatives that have that amount of ram on board .(see cygnal.com)
But if you are a student i suggest you to do at least one project using a multiplexed architecture .Then you also need some decoding logic to select your device ,in your case your memory .. There are some small srams with realtime clocks at the same time.from STmicroelectronics
Now the 8051 architecture is an old architecture ,and there are 4 address spaces
CODE ,DATA ,IDATA XDATA
so every time that you want to access a piece of data you need to indicate where it is ( by using the appropriate instruction ).. Usually with keil C compiler is very simple .by using the PRECEEDING the keyword indiating the space .Keil generates the proper instruction for accessing that SPACE .
CODE is a 64Kbytes space ,DATA is only 128 as well as IDATA .XDATA is also 64k long .. There are plenty of tricks to know about this chips .So get a book it will be better than to ask for little pieces of information here and there .!

eltonjohn said:

There are plenty of tricks to know about this chips .So get a book it will be better than to ask for little pieces of information here and there .!

Click to expand...

Normally information provided in many books available at least in our area deals with the the wider aspects of the subject. But if I can get the correct details of a chip normally used by experienced design engineers in our board , at least I can save a lot of time. None of the derivatives of 8051 with more than 256 RAM is available for me here. Offcourse, Now I will look for one elsewhere.
Little pieces of information provided through the board are very vital for newbies like me. The informations may be everywhere but locating them easily is the task. After all helping in that aspect also may be one of the objectives of our Board.
Thank you
Picstudent

Picstudent,

if you do not already have it get the book "The final word on the 8051" from here:
https://www.8052.it/download.htm

You can also get other nice goodies for the 8051 from this site.

And are you really sure that you can not get 89C51RD2 from Philips or AT89C51RD2 from Atmel in your contry?

Because both chips have 1K Xdata memory integrated so you would not need any glue logic for operation ...

best regards

C-Man said:

Picstudent,
if you do not already have it get the book "The final word on the 8051" from here:
h**p://www.8052.it/download.htm
And are you really sure that you can not get 89C51RD2 from Philips or AT89C51RD2 from Atmel in your contry?
best regards

Click to expand...

Thanks for the link.
The chip may be available in my country But in metros only. They wont send few pieces to my place.( normally my experience!)

Thanks again let me see.
I have done the moving display posted in our board by 'ROJO'.
It was ported to a Cygnal development kit which has got XRAM of 4K inside. Now I want to move that programe to a 89S51 board. Ir requires some extra ram or else display length has to be reduced .

Thank you

Picstudent