Hi, I'm using Silabs IDE and KEIL C51. I need to modify the PUTCHAR.C and to add it in my project. The problem is, in my MAIN.C file I have declared a circular ring buffer (I'm using the buffer for UART transmit) wich is delared: xdata RingBuf rbTX0; // Transmit buffer But in the PUTCHAR.C I'm writing to this buffer. The problem is when I compile I get an error POINTER TO DIFFERENT OBJECT. I have added the putchar.c to my project. So how can I use a variable in a file that was declared in an other file ? Thanks, Aldrin,