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How to use 8051 to handle about 1MB of memory?

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john2020

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Dear All,

Im trying to use the 8051 to handle memory about 1MB.
Any one know how the idea to handle this, or maybe you

can tell me, where i can find the document that
explain about this.

Thanks.

john
 

r_p_sanna

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8051 more than 64K

I dont think you ll get 8051 more than 64 K.
 

klystron

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Re: 8051 more than 64K

For more than 64k external RAM use an I/O pin as adress line 17 to switch between two 64k banks of RAM. Using multiple I/O pins the RAM size can be increased to 1 M.
Take a look at the ADUC812 ; it can address 16 M of RAM
 

john2020

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Re: 8051 more than 64K

hi klystron


Unless your processor handles that amount of memory (it doesn't) your
only recourse is to use bank switching. You'll have to design the
memory access mechanism so that you can have some part of the large
space visible in a "page" and then switch from page to page as you
need it.

The page size that you choose depends on how much of the memory space
you need for other purposes. Generally, the larger your page size the
less page switching you'll be doing. Also, you could bank switch into
either data memory or program memory or, perhaps both depending on
your needs.


regards
john
 

wek

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8051 more than 64K

Now this is a very interesting situation, john2020 asking for some basic help and finally john2020 explaining it in detail... ?

wek
 

Bus Master

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Re: 8051 more than 64K

Do you need a 1MB RAM or Code memory? if RAM you can address as much as you need by following these steps:

1) connect the databus of the BLOCK RAM to a port buffer chip.
2) connect the same port to as many I/Ps of an address bus latch chips (e.g. 74F373)

3) By writing the required address to Latches chips, you can read/write data bytes through the same port after activating the control pins (R/W, CE) of the BLOCK RAM

By using this technique, i was able to interface a 6MB static RAM to an ordinary 8051 controller.
 

maadi

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Re: 8051 more than 64K

use memory mapping technique but u would loose some ports
 

afti_khan

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Re: 8051 more than 64K

u have to use memory mapping and u'll have to use 4 bits of some other port ( like port 1 or port 3)
 

z81203

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8051 more than 64K

check dallas 320 series.
 

ntfreak

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Re: 8051 more than 64K

A simple solution is to use the ST UPSD range, they have a embedded cpld which takes care of all the pain with larger mem sizes.

www.st.com/upsd

Regards
NTfreak
 

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