#17229 - ironblood - Thu Mar 04, 2004 3:03 pm
Hi, everyone. I am a GBA newbie.
I wonder if it's possible to build a large size sram like 8MByte in a cartridge and the rest 24MByte space is used by a flash memory. If possible, could this 8Mbyte space be read/write in a speed as the internal and external RAM?
Is any known workaround?
Thanks.
#17232 - ampz - Thu Mar 04, 2004 6:04 pm
Yes, it is possible to build such a cartridge. Read and write speeds with 2/1 waitstates would be possible. That is slightly faster than external RAM, but much slower than internal RAM.
There is however one small limitation: 8bit writes are not allowed.
It is not possible to do a quick hack and get this configuration. It must be developed from scratch.
I can do it for you if you represent a company and need this special cart configuration for a product.
#17259 - ironblood - Fri Mar 05, 2004 4:05 am
Thank you for your answer, ampz.
And I still have a question. If a cartridge is built with 8Mbyte SRAM and 24Mbyte flash memory, how are they mapped into the memory space?Could CPU access them by reading/writing from/to the address straitforward?
#17260 - tepples - Fri Mar 05, 2004 4:48 am
If they run at the same speed, you'll be able to access them in 0x08000000-0x09ffffff as you expect.
However, if they run at different speeds, you'll probably want to access them in 0x08000000-0x097fffff for ROM and 0x0d800000-0x0dffffff for SRAM.
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#17262 - ironblood - Fri Mar 05, 2004 5:32 am
Thank you, tepples
#17267 - ampz - Fri Mar 05, 2004 2:33 pm
Exactly.