User Manual
623
Rev. 1.1
2019-03-18
TLE984xQX
Microcontroller with LIN and Power Switches for Automotive Applications
UART1/UART2
19.2.1
Block Diagram
Figure 162 UART Block Diagram
19.3
UART Modes
The UART1/UART2 can be used in four different modes. In mode 0, it operates as an 8-Bit shift register. In mode
1, it operates as an 8-Bit serial port. In modes 2 and 3, it operates as a 9-Bit serial port. The only difference
between mode 2 and mode 3 is the baud rate, which is fixed in mode 2 but variable in mode 3. The variable
baud rate is set by the underflow rate on the dedicated baud-rate generator.
The different modes are selected by setting bits SM0 and SM1 to their corresponding values, as shown in
Mode 1 example: 8 data bits, 1 start bit, 1 stop bit, no parity selection, 16 times oversampled (majority decision
of bits 6, 7, 8), receive & transmit register double buffered, Tx/Rx IRQ(s).
19.3.1
Mode 0, 8-Bit Shift Register, Fixed Baud Rate
In mode 0, the serial port behaves as an 8-bit shift register. Data is shifted in through RXD, and out through
RXDO, while the TXD line is used to provide a shift clock which can be used by external devices to clock data in
and out.
The transmission cycle is activated by a write to SBUF. The data will be written to the transmit shift register
with a 1 at the 9th bit position. For the next seven machine cycles, the contents of the transmit shift register
are shifted right one position and a zero shifted in from the left so that when the MSB of the data byte is at the
Table 330 UART
Modes
SM0
SM1
Operating Mode
Baud Rate
0
0
Mode 0: 8-Bit shift register
f
sys
/2
0
1
Mode 1: 8-Bit shift UART
Variable
1
0
Mode 2: 9-Bit shift UART
f
sys
/64 or
f
sys
/32
1
1
Mode 3: 9-Bit shift UART
Variable
SCU_DM
UART disreq from SCU _DM
UART
Module
RI
TI
Clock
Control
Address
Decoder
f
UART2
SCU_D
M
Interrupt
Control
UART
AHB Interface
RXD
TXD
Port Control
GPIOs
f
BR
Baud Rate
Generator
URIOS
TXD
RXD_1
SCU_DM
RXDO_2
P0.x
P1.x
P2.x
RXD_0