Hello
please let me know, edit external memory AT 89c51 from WR and RD pin, ( schematic comunications with PC to pin RD and WR AT 89c51 ) and software please.
thanks Ahmad
Note that you need C51 for an AT89c51 - not C251!
The information you require is in the so-called "bible" for the 8051:
Chapter 1 - 80C51 Family Architecture: www.nxp.com/.../80C51_FAM_ARCH_1.pdf
Chapter 2 - 80C51 Family Programmer's Guide and Instruction Set: www.nxp.com/.../80C51_FAM_PROG_GUIDE_1.pdf
Chapter 3 - 80C51 Family Hardware Description: www.nxp.com/.../80C51_FAM_HARDWARE_1.pdf
See also: http://www.8052.com/faqs
Many development board suppliers - including Keil - publish the schematics of their designs; so you can look at them for examples
eg: http://www.8052.com/sbc/ http://www.keil.com/boards/