INTERNAL SPECIFICATIONS1194.6.3.4 Mode 34.6.3.4.1 OutlineMode 3 is another 11-bit frame UART mode (with one start bit, eight data bits, one multi-purpose data bit, and one stop bit). Whereas the baud rate is 1/64th or 1/32nd of thefundamental oscillator frequency in mode 2, the mode 3 baud rate can be freely selectedaccording to the timer/counter 1 or timer/counter 2 setting. Apart from the ability to vary thebaud rate, mode 3 is identical to mode 2.A block diagram of the serial port in mode 3 is shown in Figure 4-35, and the operational timingchart is given in Figure 4-36.4.6.3.4.2 Mode 3 baud rateAs in mode 1, the timer/counter 1 or timer/counter 2 overflow can be set as the baud rate clocksource in mode 3 by independent TCLK and RCLK setting for the transmit and receivecircuits.Where the baud rate is determined by the timer/counter 1 overflow, baud rate is determinedby the overflow frequency and SMOD value according to the following equations.B = fTC1 × 21 × (SMOD=0)B = fTC1 × (SMOD=1)161161Where B is the baud rate and fTC1 is the timer/counter 1 overflow frequency.When timer/counter 1 is used as a timer in auto reload mode (mode 2), the baud rate isdetermined by the following equations.B = fOSC × 256-DTH11× (SMOD=0)(SMOD=1)12121× 161×B = fOSC × 256-DTH11×121 × 161where B is the baud rate, fOSC the fundamental oscillator (XTAL1·2) frequency, and DTH1 theTH1 contents (expressed in decimal).Where the timer/counter 2 overflow serves as the baud rate clock source, the baud rate isdetermined by the overflow frequency irrespective of the SMOD value.When timer/counter 2 is used as a counter, the baud rate is determined by the followingequation.B = fT2 × 65536-DRCAP21 × 161where B is the baud rate, f T2 the frequency of the clock applied to the T2 pin, and DRCAP2 thecontents of RCAP2L and R CAP2H (expressed in decimal).Or if timer/counter 2 is used as a timer, the baud rate is determined by the following way.
