I have a DS80C400 with external Flash ROM and external SRAM. I have succesfully generated a HEX file with the Keil compiler and can run this when the nEA pin is low. (Disables access to built in ROM functions) However I wish to use the built in bootloader and (according to the DS80C400 datasheet Table 12 [page 70]) I therefore need to have the nEA pin pulled high so that the bootloader will operate when required. My problem occurs when I go through the bootloader and enter the command 'E' to trigger the find user code routine, I am presented with the error "No User Code, Halting System". For this to operate my bank of code needs to begin with an SJMP to bypass the signature byte and then have a signature of the four ascii bytes T I N and I. Q1. Does Keil have the facility to insert this signature byte? Q2. Would such a signature interfere with the ISR lookup table which I beleive to be stored at the start of the ROM?