If you want to call assembly routine phread from C with parameter hello make a C function "void phread(hello){}" and use the generated assembler as a template for the framework of the assembler routine.

If you have problems with the above, you are using a just plain too old version. Did the SRC directive exist in antiquity? I do not know. In the days when Keil was sold as Franklin, I used other brands because Franklin was "whatever". There is no guarantee that your Franklin is a Keil, it can be one of about 4 different brands rebranded.

What are you doing? you will get NOWHERE running all over fooling with BASIC, C and assembler. Drop either BASIC or C and assembler unless, of course, you have 20 years experience in both.

Erik