In SX Microcontrollers, SX/B Compiler and SX-Key Tool, PJ Allen wrote: OK, thanks, Bean. There we read: The PROGRAM directive sets the execution start point (at a label.) When the NOSTARTUP option is used the SXB compiler will NOT insert the normal start-up code that pre-initializes all RAM addrs to zero; in this case the programmer is responsible for appropriate initialization... Note that when the NOSTARTUP option is used the TRIS registers are NOT initialized, so you MUST set up the ports as INPUTs or OUTPUTs. djh82uk's program has the NOSTARTUP option. So, even though somebody uses: InPin PIN RA.0 INPUT CMOS OutPin PIN RA.1 OUTPUT