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Hi,im used project with 512k extern RAM,for 512bytes on-chip ram, can anyone show me any advice about this?
Bank switching logic is not really something you set up in the IDE, but on the actual hardware. It's additional circuitry you must have on your PCB, situated between the micro and the RAM chips. Once you're sure you have managed that part, you can look into the manual to see how to tell Keil tools about XDATA banking. See the paragraph about XBANKING.A51, in particular.
I really have actual hardware in PCB, with 3 bits I/O pins switching 512k extern ram,AND with dual-DPTR,where and which shouldbe set in XBANK.A51,only this file can be sure work? Thanks, John
You'll now have to implement the functions the manual requires XBANKING.A51 to supply. Essentially, those will all be short assembler functions. At the minimum, that'll mean you have to adapt the default implementation provided by Keil, telling it which register serves as "DPX", the most significant byte of 3-byte addresses. Also see the VARBANKING directive (or its equivalent options in uVision2), and the example of this pointed at in the manual.