I've monitor program which will wait for code to be download. And when download finished it'll jump to address 4000H. I'd tried to set code address option in uVision to start at 4000h. But in the hex file there's code like this
:0300000002443780 :0C443700787FE4F6D8FD75812102440E68 :10400000E517240BF8E60517227808300702780B2D :10401000E475F0011243B10243592000EB7F2ED228
:03400000024437XX :0C44370078XXXXXXXXXXXXXXXXX :10400300XXXXXXXXXX
It's been a while since I worked on 8051, but is the first hex record establishing the reset vector at address 0?