Hello, Configuration: uVision2, Compiler 6.20a. When I look into the reg52.h-file (inc directory), then I see for the alternative port pins P3.4 and P3.5 the following definition: sbit T1 = P3^5; sbit T0 = P3^4; However, if I look into the data handbook of Philips (book IC20 - 1991, page 154), then I see that the bits for T1 and T0 are reversed. So, in that book they are defined as follows: sbit T0 = P3^5; sbit T1 = P3^4; Which one is right: the .h-file or the data book? Rgds, Geert