C8051F340 Datasheet, PDF (211/282 Pages) List of Unclassifed Manufacturers – Full Speed USB Flash MCU Family

C8051F340/1/2/3/4/5/6/7
18. UART0
UART0 is an asynchronous, full duplex serial port offering modes 1 and 3 of the standard 8051 UART.
Enhanced baud rate support allows a wide range of clock sources to generate standard baud rates (details
in Section “18.1. Enhanced Baud Rate Generation” on page 212). Received data buffering allows
UART0 to start reception of a second incoming data byte before software has finished reading the previous
data byte.
UART0 has two associated SFRs: Serial Control Register 0 (SCON0) and Serial Data Buffer 0 (SBUF0).
The single SBUF0 location provides access to both transmit and receive registers. Writes to SBUF0
always access the Transmit register. Reads of SBUF0 always access the buffered Receive register;
it is not possible to read data from the Transmit register.
With UART0 interrupts enabled, an interrupt is generated each time a transmit is completed (TI0 is set in
SCON0), or a data byte has been received (RI0 is set in SCON0). The UART0 interrupt flags are not
cleared by hardware when the CPU vectors to the interrupt service routine. They must be cleared manually
by software, allowing software to determine the cause of the UART0 interrupt (transmit complete or receive
complete).
UART0 Baud
Rate Generator
SFR Bus
Write to
SBUF0
TB80
SET
D
Q
CLR
SBUF0
(TX Shift)
Zero Detector
Stop Bit
Start
Tx Clock
Shift
Tx Control
Data
Send
Tx IRQ
SCON
TI0
RI0
TX0
Crossbar
Serial
Port
Interrupt
Port I/O
Rx Clock
Start
Shift
Rx IRQ
Rx Control
0x1FF
RB80
Load
SBUF0
Input Shift Register
(9 bits)
Load SBUF0
SBUF0
(RX Latch)
Read
SBUF0
SFR Bus
RX0
Crossbar
Figure 18.1. UART0 Block Diagram
Rev. 0.5
211