Personally, I shy away from using POP and PUSH for storing data in RAM. Too many other things going on in the stack when using interrupts and CALLS. Unless you require the use of Register Banks 1,2, and 3, I would leave the stack pointer at its default value (07h). In your code it seems as though you have set it near the top of user space which could cause problems. Remember, in an 8051 the stack grows upward as it is used. As for MSG4 I would define either R0 or R1 as MSG4 and use it as an indirect pointer to ram for your SBUF data. You could initialize MSG4 to 30h and store your incoming message there. You will probably need to add another LCD display routine to deal with data from ram since your current routine will only display data from code memory.

Hal