Hi Experts, I'm using an 80C31 processor (11.0592 MHz xtal) with a very simple memory model:- a 32K Rom installed at from 0x0000 to 0x7FFF and a 32K SRAM at 0x8000 to 0xFFFF. MON51 configured as : INSTALL 0 FF 00 and INSTALL.A51 modified as : INT_ADR_OFF EQU 8000H ; INTERRUPT VECTOR OFFSET IF MONITOR ; IS INSTALLED AT ADDRESS 0000H DEF_PC_VAL EQU 8000H ; DEFAULT PC VALUE AFTER START UP The project set up as:- Target Tab: 1) off chip code memory Eprom Start 0x0000 Size 0x7FFF 2) off chip Xdata memory Ram Start 0x8000 Size 0x7FFF C51 Tab: Interrupt vector at address: 0x8000 BL51 Locate Tab: 1)Checked Use memory layout from target dialog Left all other fields blank Debug Tab: Checked Use Keil mon-51 Driver and Load application at startup. Changed CSEG AT 8000H in the STARTUP.A51 file and added this file to the project. When clicked on Debug->Start/Stop Debug Session in the output window showed that Connected Target to MON51 and Monitor Error No Code At 0x0000. Anything else for this set up that I did not follow or missed out? Any help is appreciated. I really want to try this product. Thanks Joseph Phan