Hello, I spent a lot of time to solve the problem but I'm dumb. I modified the INT_ADR_OFF=4000h and the DEF_PC_VAL=4000h and compiled with the following command line parameter install 8 0 0 which means autobaud code start at 0 and xdata at 0. My system has ROM from 0-3fff RAM 0-3fff as xdata and 4000-7fff as user code area. When I started to try the monitor id didn't work. The connection was succesfull but when I try to download a program I get an error message there is no RAM at 0. The PC value on the screen was permanently 0600h and when I tried to reset from the reset button on the screen it showed 600h again. Help me please. Cheer George
You should read the information provided in the C51 User's Guide, Appendix F, Using Monitor-51. It discusses the settings required when Monitor-51 is installed at 0.