W79E201 Datasheet, PDF (55/87 Pages) Winbond – 8-BIT MICROCONTROLLER

W79E201
This mode is similar to Mode 2 in all respects, except that the baud rate is programmable. The user
must first initialize the Serial related SFR SCON before any communication can take place. This
involves selection of the Mode and baud rate. The Timer 1 should also be initialized if modes 1 and 3
are used. In all four modes, transmission is started by any instruction that uses SBUF as a destination
register. Reception is initiated in Mode 0 by the condition RI = 0 and REN = 1. This will generate a
clock on the TxD pin and shift in 8 bits on the RxD pin. Reception is initiated in the other modes by the
incoming start bit if REN = 1. The external device will start the communication by transmitting the start
bit.
Timer 1
Overflow
2
SMOD = _{0 1}
TCLK 0
Timer 2
Overflow
Write to
SBUF
TX START
1
16
TX CLOCK
0
TB8
Internal
Data Bus
1
TX SHIFT
TI
RCLK 0 1
16
SERIAL
CONTROLLER ^RI
Transmit Shift Register
STOP
D8
PARIN SOUT
START
LOAD
CLOCK
TXD
Serial Port
Interrupt
SAMPLE
1-TO-0
DETECTOR
RXD
RX CLOCK
RX START
LOAD
SBUF
RX SHIFT
BIT
DETECTOR
CLOCK
PAROUT
SBUF
SIN
D8
RB8
Receive Shift Register
Read
SBUF
Internal
Data
Bus
Table 10. Serial Ports Modes
SM1 SM0 Mode Type
0
0
0
Synch.
0
1
1
Asynch.
1
0
2
Asynch.
1
1
3
Asynch.
Serial Port Mode 3
Baud Clock
4 or 12 TCLKS
Timer 1 or 2
32 or 64 TCLKS
Timer 1 or 2
Frame
Size
8 bits
10 bits
11 bits
11 bits
Start
Bit
No
1
1
1
Stop
Bit
No
1
1
1
9th bit
Function
None
None
0, 1
0, 1
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Publication Release Date: December 16, 2004
Revision A2