INTERNAL SPECIFICATIONS103Table 4-16 Serial port operation modesSM00011SM10101Mode0123FunctionI/O extension10-bit frame UART11-bit frame UART11-bit frame UARTBaud rate1/12 FOSCVareable1/32 FOSC or 1/64 FOSCVareableNote: FOSC denotes frequency of fundamental oscillator (XTAL1·2).4.6.2.2 SBUF (serial port buffer register)SBUF is an 8-bit special function register used to store transmitting and receiving data.Although the SBUF is specified by the same data address 99H for both writing and reading,physically separate registers are specified. That is, the sending circuit SBUF is specified byinstructions where SBUF is used as a destination operand, and the receiving circuit SBUFis specified by instructions where SBUF is used as a source operand.4.6.2.3 TCLKTCLK controls selection of the baud rate clock source for the transmitting circuit when in mode1 or 3.The timer/counter 2 overflow becomes the transmitting circuit baud rate clock source whenTCLK is set in mode 1 or 3. And the timer/counter 1 overflow becomes the transmitting circuitbaud rate clock source if TCLK is cleared.TCLK has no effect on the baud rate clock source when in mode 0 or 2. TCLK is located atbit 4 of T2CON (timer/counter 2 control register) specified by data address 0C8H. This bit canalso be specified by bit address 0CCH.4.6.2.4 RCLKRCLK controls selection of the baud rate clock source for the receiving circuit when in mode1 or 3.The timer/counter 2 overflow becomes the receiving circuit baud rate clock source whenRCLK is set in mode 1 or 3. And the timer/counter 1 overflow becomes the receiving circuitbaud rate clock source if RCLK is cleared.RCLK has no effect on the baud rate clock source when in mode 0 or 2. RCLK is located atbit 5 of T2CON (timer/counter 2 control register) specified by data address 0C8H. This bit canalso be specified by bit address 0CDH.
