Serial Port 1 (Uart1); Serial Port 1 Baud Rate Generator (S1Brg); S1Brg Configuration (S1Tme=0); Baud Rate In Mode 0 - CMOSTEK CMT2380F17 Manual

19 Serial Port 1 (UART1)

The CMT2380F17 is equipped with a secondary UART (hereafter, called UART1), which has 5 operation
modes, Mode 0 ~ Mode 4, the same as the first UART (UART0) except the following differences:
(1) The UART1 has no enhanced functions: Framing Error Detection and Auto Address Recognition.
(2) The UART1 use the dedicated Baud Rate Timer as its Baud Rate Generator (S1BRG).
(3) The UART1 uses TXD1 and RXD1 for transmit and receive, respectively.
(4) The Baud Rate Generator provides the toggle source for S1CKO and peripheral clock.
(5) S1 + S1BRG can be configured to an 8-bit auto-reload timer with port change detection.
(6) In mode 0 and mode 4, S1TX12 of UART1 is the same function as URM0X3 in UART0.
The UART1 and UART0 in CMT2380F17 can operate simultaneously in identical or different modes and
communication speeds.

19.1 Serial Port 1 Baud Rate Generator (S1BRG)

The CMT2380F17 has an embedded Baud Rate Generator to generate the UART clock for serial port 1
operation in mode 1 and mode 3. It is constructed by an 8-bit up-counter, S1BRC, and an 8-bit reload register,
S1BRT. The overflow (S1TOF) of S1BRC is the time base of UART1 serial engine in mode 1 and mode 3 and
triggers the S1BRT content reloaded into S1BRC for the consecutive counting.
If S1TR = 0, software writing S1BRT will modify S1BRC simultaneously. After S1TR enabled to start the
S1BRC counting, it is no influence on S1BRC when S1BRT is writing. Modifying S1BRC is always
independent with S1BRT content.
This baud rate generator can also provide the time base for serial port 0 by software configured. There is
an addition clock output, S1CKO, from the S1BRC overflow rate by 2 (S1TOF/2). S1TOF also supplies the
toggle source for other peripherals' clock input. Regardless S1 engine is running or pending, S1BRG always
serves the time base function for these peripherals.
The configuration of the Serial Port 1 Baud Rate Generator is shown in Figure 19–1.

19.2 S1BRG configuration (S1TME=0)

19.2.1 Baud Rate in Mode 0

Figure 19–1. S1BRGStructure(S1TME=0)
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CMT2380F17
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