hello; i m studying data sheet of c8051f020. i m confused about its memory management -it mentions that it has 64KBytes of on chip external ram -it has 4Kbytes of on-chip ram i am planning to interface 6264 to it, but what will be my starting address of it. will it be 4001H for 6264 and if yes then what about my 64KByte external ram? i am confused about 4Kbyte and 64KBytes memory. does this means that 6264 works as extension after 4KByte ram and 64Kbyte ram is seperate from it pls, correct me if i m wrong thank u all
usually you can specify differently, but the default is that the internal RAM is used till it ends and then the external RAM is, You need not to do anything if that is what you want. The part of your external RAM that matches the addresses covered by the internal RAM will be unused.
using the '020 you will, most likely, need to set the 'external data delay' SFRs to match the timing of your external RAM.
Erik
Hi Erik, Thanks for replay. But I got confused by your statements I will write what I understood from the discussion 1. if internal ram is 4Kbytes then after complting 4Kbytes on-chip external ram will be used. Is this the meaning of 1st sentence? 2. on-chip external ram is till 64Kbytes 3. it means if I interface 6264 then its address will not be 4001H,is it correct? 4. what is ‘external data delay’ SFR 5. I have studied what is should do in terms of hardware but confused about writing software 6.because on 6264 there are address, data, chip select, read/write line are present 7. and address is given by microcontroller 8. address of 6264 will be random is it like that? Pls, correct me if I m wrong Thank you again
the external RAM will be addressed in "true address" in other words XDATA 0x2345 is RAM address 0x2345. It will just be that as you have 4k (fast) internal RAM addresses 0-0x0fff will never be accessed in the external RAm.
what is ‘external data delay’ SFR EMI0CN, EMI0TC and EMI0CF
DO NOTE: you NEED to set those and the memory interface select SFR (you can find that one yourself in the datasheet) at the very beginning of startup.a51 or your C initialization WILL fail.