Hi Nigel, You can get more info if you mail to: ccs@execpc.com The CCS compiler is a easy to use compiler. But beware that the build in RS232 feature is not an interrupt driven one if the PIC you use has no uart. I'm planning to use lots of 16C84 and I want them to do more than just waiting for serial commands. So an interrupt driven RS232 serial routine must be implemented. I was thinking of rewriting the AN555(asyn. serial I/O) in C-code. In this note a lot of assembly-time calculations is done with big numbers. The css-compiler can NOT do this because of it's limited 16bit defines!. Now I'm trying to 'link' the AN555 object-code in a C-program. Also not a standard feature :-( Edwin Baaij (Electronics Engineer) ********************************************************************* University of Amsterdam phone: +31-20-5256346 Van der Waals,- ZeemanInstitute fax: +31-20-5255877 Valckenierstraat 65-67 e-mail: baaij@phys.uva.nl 1018 XE Amsterdam *********************************************************************