W79E632A Datasheet, PDF (56/79 Pages) Winbond – 8-BIT MICROCONTROLLER

W79E632A/W79L632A
1. RI must be 0 and
2. Either SM2 = 0, or the received stop bit = 1.
If these conditions are met, then the stop bit goes to RB8, the 8 data bits go into SBUF and RI is set.
Otherwise the received frame may be lost. After the middle of the stop bit, the receiver goes back to
looking for a 1-to-0 transition on the RxD pin.
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.
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
START ^SOUT
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
Table 10. Serial Ports Modes
SM1 SM0 MODE
0
0
0
0
1
1
1
0
2
1
1
3
TYPE
Synch.
Asynch.
Asynch.
Asynch.
Figure 23. 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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