;;; RS-485 SERIAL COMMUNICATIONS.;;; Modes:;;; (1) Receive data (REN = 1, T0 = 0, SM2 = 1);;; (2) Send data    (REM = 0, T0 = 1)SetPort:   mov SCON, #11000000b ;;; Serial comm: 9 bits, no parity, 1 stop bit.      clr PS   clr RCLK   clr TCLK   mov A, TMOD   anl A, #00001111b   add A, #00100000b ;;; Timer 1: baud rate timer.   mov TMOD, A   mov TH1, #-3         ;;; Baud rate: 19200 baud.   setb TR1   clr TB8   clr RI   clr TI   setb SM2   setb ESretgetchar:   jnb T0, InRx      clr T0    ;;; Set mode for "Receive data"      setb REN   InRx:   mov R0, #SP_RI   acall Pause   mov A, SBUFjnb ACC.6, getchar   anl A, #00111111bretputchar:   jb T0, InTx      mov R6, #100 ;;; Set mode for "Send data"      djnz R6, $   ;;; Wait 201 cycles for other end to release the line.      clr REN      setb T0   InTx:   mov SBUF, A   mov R0, #SP_TI   acall Pauseret