UPSD3422_06 Datasheet, PDF (105/293 Pages) STMicroelectronics – Turbo Plus Series Fast Turbo 8032 MCU with USB and Programmable Logic

uPSD34xx
Serial UART interfaces
Figure 31. UART mode 0, block diagram
Write
to
SBUF
Internal Bus
D SQ
CL
SBUF
Zero Detector
fOSC/12
REN
R1
Start
Tx Clock
Tx Control
T
Shift
Send
Serial
Port
Interrupt
Rx Clock
Start
R
Receive
Rx Control
Shift
76543210
Load
SBUF
Read
SBUF
Input Shift Register
SBUF
Shift
Internal Bus
RxD
Pin
Shift
Clock
TxD
Pin
RxD
P3.0 Alt
Input
Function
AI06824
Figure 32. UART Mode 0, Timing Diagram
Write to SBUF
Send
Shift
RxD (Data Out)
TxD (Shift Clock)
TI
Write to SCON
RI
Receive
Shift
RxD (Data In)
TxD (Shift Clock)
D0
D1
D2
D3
D4
D5
D6
D7
Clear RI
D0
D1
D2
D3
D4
D5
D6
D7
Transmit
Receive
AI06825
21.5
More about UART mode 1
Refer to the block diagram in Figure 33 on page 107, and timing diagram in Figure 34 on
page 107.
Transmission is initiated by any instruction which writes to SBUF. At the end of a write
operation to SBUF, a '1' is loaded into the 9th position of the transmit shift register and flags
the TX Control unit that a transmission is requested. Transmission actually starts at the end
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