W77L32 Datasheet, PDF (63/76 Pages) Winbond – 8-BIT MICROCONTROLLER

W77L32/W77L032A/W77M032A
11.6.4 Mode 3
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.
Table 10. Serial Ports Modes
SM1 SM0 MODE TYPE
0
0
0
1
1
0
1
1
0
Synch.
1
Asynch.
2
Asynch.
3
Asynch.
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
Timer 1
Overflow
Timer 2 Overflow
(for Serial Port 0 only)
÷2
Write to
SBUF
TB8
Internal
Data Bus
SMOD=
(SMOD_1) ⁰
1
TCLK _{0 1}
÷16
TX START TX SHIFT
TX CLOCK
TI
RCLK
01
÷16
SERIAL
CONTROLLER ^RI
SAMPLE
1-TO-0
DETECTOR
RX CLOCK
RX
START
LOAD
SBUF
RX SHIFT
STOP
D8
PARIN
SOUT
START
LOAD
CLOCK
Transmit Shift Register
TXD
Serial Port
Interrupt
Read
SBUF
RXD
BIT
DETECTOR
CLOCK
PAROUT
SBUF
SIN
D8
RB8
Receive Shift Register
Internal
Data
Bus
Figure 23: Serial Port Mode 3
- 63 -
Publication Release Date: April 17, 2007
Revision A6