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.
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.
Hi, you just use spare i/o pins to select another rom bank. If you need that much memory you should consider changing to a bigger processor.
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
use a latch. Plenty of examples on the web
use an 8255 ?
or use a dallas 80c400 can access up to 16MB of external memory may be a bit of overkill
use a cpld
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
or other good 8051 book as most should have examples of what you want in them.
Alex Gibson
For what purpose ?? Code ? Data ? tables ?
Will a serial device work for your application ?
please be more specific with your requirements..
Most 8052 devices have 16 address lines. Are you using a non standard 8052 ?? Which manufacture ??
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 )
In article , John Tan writes
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 /\/\/\/\/\ /\/\/ snipped-for-privacy@phaedsys.org
Good point... I missed that!!
Why do you need 512 of ROM?
Yes!!! /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ \/\/\/\/\ Chris Hills Staffs England /\/\/\/\/\ /\/\/ snipped-for-privacy@phaedsys.org
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.