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hello everyone, i am using 89c51 interfacing with 6264
in 89c51 we have ram = 4Kbyte i.e for the further size i need to switch to 6264
total address line on 6264= 12 so A15=/CS1=0 A14=CS2=1 A13= gnd=0 A0-A7 = P0.0 to P0.7 of 89c51 trough latch A8-A12 = P2.0 to P2.4 of 89c51 D0-D7=P1 for data /WE = /we of 89c51 /RD = /Rd of 89c51 ALE connected to clk of latch this is my hardware
now i have sstarted programming in c i am using _at_ for the address what all care i should take to select 6264 i have taken care of A15,A14,A13 and ALE can u show me sample code for it 4000 is intermal ram and for external it is 4001 address what if i select 4000 for external ram, does it conflict with internal ram as soon as i transfer address does data is passed immediately? thank u in advance for further inputs from me pls let me konw
If the internal ram is 0x4000 large, then it isn't likely to end at address 0x4000, but at address 0x3fff, i.e. leaving address 0x4000 as the first free address.
But the data sheet for your processor should normally tell you these kind of things.
hello, thank you for reply i am going through datasheet can you give me any link for c program of external ram interface because i am confused with memory access code pls suggest me thank you
It is irrelevant to the 'C' program!
As far as the 'C' program is concerned, it's all just XDATA - it's up to your hardware to make the interface.
You just need to tell the Linker what memory address ranges your target hardware has available - see: www.keil.com/.../uv3_ca_ovwconfigdialogs.htm
Your Startup code might need to do some things to correctly configure your hardware: http://www.keil.com/support/man/docs/c51/c51_ap_startup.htm
Have you actually worked through (not just read) the basic examples: http://www.keil.com/support/man/docs/uv3/uv3_examples.htm ?
hello; thanx for replay i tried small program in c can you tell me how to differentiate between on-chip ram and off-chip external ram i.e if int ram address is =0000 to 3fff then for address 4000 will be diverted to external off-chip ram does this happen automatically? or we have to write code for it? what is differnce between: volatile unsigned char xdata ADD1 _at_ 0x4000 and unsigned char xdata ADD2 _at_ 0x4000 i tried this and i got warning as xdata space memory overlap is there any conflict if we enter same address for both on-chip and off-chip external ram please,correct me if i am wrong thank you all
You will have to study the Datasheet to answer that!
It depends on the chip, and how you configure it!
what is differnce between:
volatile unsigned char xdata ADD1 _at_ 0x4000
and
unsigned char xdata ADD2 _at_ 0x4000
The difference is, obviously, that one contains 'volatile' and the other doesn't!
'volatile' is a standard 'C' keyword - so you can look it up in any 'C' textbook.
"i tried this and i got warning as xdata space memory overlap"
Of course you did! If you define two things at the same address then they will, by definition, overlap - won't they?!