Forums

Extra addr. lines needed

Started by John Tan December 29, 2003
Hi,
I'm using an 8052 that has 12 addr lines ~ 4KB of addressable space.
But i need to access additional 512KB of ROM ~ 19 address lines
required!

How do i extend the addr. to 19 lines.

Can i do this:

1) get firmware engineer to extend it using GPIO pins ? Is this a good
method ?
2) some kind of paging access ? how exactly, i not too sure in terms
of HW wiring ?

Thanks.
John Tan wrote:
> Hi, > I'm using an 8052 that has 12 addr lines ~ 4KB of addressable space. > But i need to access additional 512KB of ROM ~ 19 address lines > required! > > How do i extend the addr. to 19 lines. > > Can i do this: > > 1) get firmware engineer to extend it using GPIO pins ? Is this a good > method ? > 2) some kind of paging access ? how exactly, i not too sure in terms > of HW wiring ? > >
Depends on what you are doing. If it's for table lookup or similar, you are OK, just hang some latches on the data bus and write the higher address to them. If it's for program, it's still possible but will be a real pain- you will have to link the program as separate standalone chunks overlaying the same addresses, then have some calling program in a fixed address space to sort the lot out. Interrupts will become a nightmare. Get another processor. Paul Burke
"John Tan" <bktan1974@netscape.net> wrote in message
news:eb4dd21b.0312282309.5d0e6d0d@posting.google.com...
> Hi, > I'm using an 8052 that has 12 addr lines ~ 4KB of addressable space. > But i need to access additional 512KB of ROM ~ 19 address lines > required! > > How do i extend the addr. to 19 lines. > > Can i do this: > > 1) get firmware engineer to extend it using GPIO pins ? Is this a good > method ? > 2) some kind of paging access ? how exactly, i not too sure in terms > of HW wiring ? > > Thanks.
use a latch. Plenty of examples on the web http://www.8052.com/faq.phtml?FAQ=67 www.8052.com has a good tutorial use an 8255 ? http://www.pjrc.com/tech/8051/board4/82c55.html http://www.csee.umbc.edu/~plusquel/310/slides/8086_IO2.html or use a dallas 80c400 can access up to 16MB of external memory may be a bit of overkill http://www.circuitcellar.com/library/print/0403/Cantrell153-s/5.htm use a cpld http://www.8052.com/tutflash.phtml if you chip has i2c or spi use spi or i2c eeprom or flash May be worth getting a copy of Jan Axelson's The Microcontroller Idea Book Circuits, Programs, & Applications featuring the 8052-BASIC Microcontroller even if your not using basic http://www.lvr.com/microc.htm http://www.lvr.com/microcib.htm or other good 8051 book as most should have examples of what you want in them. Alex Gibson
"John Tan" <bktan1974@netscape.net> wrote in message
news:eb4dd21b.0312282309.5d0e6d0d@posting.google.com...
> Hi, > I'm using an 8052 that has 12 addr lines ~ 4KB of addressable space. > But i need to access additional 512KB of ROM ~ 19 address lines > required! > > How do i extend the addr. to 19 lines. > > Can i do this: > > 1) get firmware engineer to extend it using GPIO pins ? Is this a good > method ? > 2) some kind of paging access ? how exactly, i not too sure in terms > of HW wiring ? > > Thanks.
For what purpose ?? Code ? Data ? tables ? Will a serial device work for your application ? please be more specific with your requirements..
TheDoc wrote:

> "John Tan" <bktan1974@netscape.net> wrote in message > news:eb4dd21b.0312282309.5d0e6d0d@posting.google.com... > >>Hi, >>I'm using an 8052 that has 12 addr lines ~ 4KB of addressable space.
Most 8052 devices have 16 address lines. Are you using a non standard 8052 ?? Which manufacture ??
>>But i need to access additional 512KB of ROM ~ 19 address lines >>required! >> >>How do i extend the addr. to 19 lines. >> >>Can i do this: >> >>1) get firmware engineer to extend it using GPIO pins ? Is this a good >>method ? >>2) some kind of paging access ? how exactly, i not too sure in terms >>of HW wiring ? >>
Either way its paging. If its only for data storage / retrieval paging is good. Just keep track of which page your on. If its for code, your interrupts and calls need to know about paging. ( not so simple )
>>Thanks. > > > For what purpose ?? > Code ? Data ? tables ? > > Will a serial device work for your application ? > > please be more specific with your requirements.. >
In article <eb4dd21b.0312282309.5d0e6d0d@posting.google.com>, John Tan
<bktan1974@netscape.net> writes
>Hi, >I'm using an 8052 that has 12 addr lines ~ 4KB of addressable space. >But i need to access additional 512KB of ROM ~ 19 address lines >required! > >How do i extend the addr. to 19 lines. > >Can i do this: > >1) get firmware engineer to extend it using GPIO pins ? Is this a good >method ? >2) some kind of paging access ? how exactly, i not too sure in terms >of HW wiring ? > >Thanks.
1 why? 2 Use something more suitable 3 use a Philps MX type that has 24 bit addressing. 4 yes to 1 and 2 They are effectively the same thing. Which compiler are you using. ? /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ \/\/\/\/\ Chris Hills Staffs England /\/\/\/\/\ /\/\/ chris@phaedsys.org www.phaedsys.org \/\/ \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
In article <3ff1e535$1_3@omega.dimensional.com>, hamilton
<hamilton@deminsional.com> writes
>TheDoc wrote: > >> "John Tan" <bktan1974@netscape.net> wrote in message >> news:eb4dd21b.0312282309.5d0e6d0d@posting.google.com... >> >>>Hi, >>>I'm using an 8052 that has 12 addr lines ~ 4KB of addressable space. > >Most 8052 devices have 16 address lines. Are you using a non >standard 8052 ?? Which manufacture ??
Good point... I missed that!!
>>>But i need to access additional 512KB of ROM ~ 19 address lines >>>required!
Why do you need 512 of ROM?
>> please be more specific with your requirements..
Yes!!! /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ \/\/\/\/\ Chris Hills Staffs England /\/\/\/\/\ /\/\/ chris@phaedsys.org www.phaedsys.org \/\/ \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/