problem in using EPROM 27C256 with 8051 microcontroller

i m using EPROM 27C256 and RAM 6264 with intel 8051 microcontroller . plz tell me how to interface this with microcontroller . plz also tell me that how the code in EPROM will be executed and how i save data in RAM and plz provide me a small code in C language for doing this. also tell me that the read/write signal will be gnerated by microcontroller itself or in programming . i m doing a very simple program but it does not work . plz provide me the interface diagram and a code for running.

This extracted figure of the book

The 8051 Microcontroller
ARCHITECTURE, PROGRAMMING, and APPLICATIONS
Kenneth J. Ayala

contains the hardware that you request.

Regards

Control signals such as PSEN (for reading code from EPROM), /WR and /RD (for writing and reading to/from RAM) are generated automatically by microcontroller.
Program from external EPROM is executed only when pin EA is connected to 0V, and it is executed in the same way as from internal program memory (if exists) with timing differences, as the micro first has to send A0-A7 on A/D bus and latch it in 74373 latch, and then in the second phase read a byte of code from EPROM.
As far as reading from or writing to RAM is concerned you can use the assembly code MOVX instruction to performe these operations. If, for example, you would like to read RAM location 0010h you can do it in the following way:
#asem
MOV DPTR, #0010h
MOVX A, @DPTR
#endasem
and A will contain the relevant value..
If you want to save value from A in RAM's location 0101h, you can do it in the fllowing way:
#asem
MOV DPTR, #0101h
MOVX @DPTR, A
#endasem
Regards,
IanP

This is a schematic of complete 80C51 with EPROM and SRAM, I have tested and it is running well. hope this can help You.


Siswanto
DigitalMax@plasa.com