CHAPTER 12 SERIAL INTERFACE UART0User’s Manual U16227EJ2V0UD25612.4.3 Dedicated baud rate generatorThe dedicated baud rate generator consists of a source clock selector and a 5-bit programmable counter, andgenerates a serial clock for transmission/reception of UART0.Separate 5-bit counters are provided for transmission and reception.(1) Configuration of baud rate generator• Base clockThe clock selected by bits 7 and 6 (TPS01 and TPS00) of baud rate generator control register 0 (BRGC0) issupplied to each module when bit 7 (POWER0) of asynchronous serial interface operation mode register 0(ASIM0) is 1. This clock is called the base clock and its frequency is called f XCLK0 . The base clock is fixedto low level when POWER0 = 0.• Transmission counterThis counter stops operation, cleared to 0, when bit 7 (POWER0) or bit 6 (TXE0) of asynchronous serialinterface operation mode register 0 (ASIM0) is 0.It starts counting when POWER0 = 1 and TXE0 = 1.The counter is cleared to 0 when the first data transmitted is written to transmit shift register 0 (TXS0).• Reception counterThis counter stops operation, cleared to 0, when bit 7 (POWER0) or bit 5 (RXE0) of asynchronous serialinterface operation mode register 0 (ASIM0) is 0.It starts counting when the start bit has been detected.The counter stops operation after one frame has been received, until the next start bit is detected.Figure 12-11. Configuration of Baud Rate Generatorf XCLK0SelectorPOWER05-bit counterMatch detector Baud rateBRGC0: MDL04 to MDL001/2POWER0, TXE0 (or RXE0)BRGC0: TPS01, TPS008-bit timer/event counter50 outputfX/2 5f X /2fX/2 3Baud rate generatorRemark POWER0: Bit 7 of asynchronous serial interface operation mode register 0 (ASIM0)TXE0: Bit 6 of ASIM0RXE0: Bit 5 of ASIM0BRGC0: Baud rate generator control register 0
