I tried to write a simple program, which is use the serial port, and send something to the computer, but it doesn't work! I got some error message after the compile! The code should be good, because if I choose an another chip in the Options/Compiler/Misc, the code can be compiled!
As you probably know the DS89C420 has two serial ports.
All the SFR involved in serial communication has either 0 or 1 suffix:
SCON0
SCON1
SBUF0
SBUF1
It's true that at SFR addr 98h we'll find SCON0 for DS89C420 and SCON for 8051.
But BASCOM didn't find any declarations inside included 89c420.dat file regarding SCON or SBUF.
That's why you have errors when compiling for 89C420 and none for 8051.
Thus if you write JNB SCON0.1 or better JNB RI_0 you can pass over error 119.
Same is true for MOV SBUF0 and MOV SCON0 or use suffix 1 for serial port 1, MOV SBUF1......