W77C32_07 Datasheet, PDF (62/78 Pages) Winbond – 8-BIT MICROCONTROLLER

W77C32/W77C032A
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.
Clock Source
Mode input
div. by 4 osc/2
div. by 64 osc/32
div. by 1024 osc/512
÷2≅⎟6Χ
Write to
SBUF
TB8
Internal
Data Bus
SMOD= _{0 1}
(SMOD_1)
÷16
÷16
SAMPLE
1-TO-0
DETECTOR
TX START
TX CLOCK
TX
SHIFT
TI
SERIAL
CONTROLLER _RI
RX CLOCK
RX START
LOAD
SBUF
RX SHIFT
RXD
BIT
DETECTOR
D8
STOP
PARIN
START SOUT
LOAD
T
CLOCK
Transmit Shift Register
TXD
Serial Port
Interrupt
CLOCK
PAROUT
SBUF
SIN
D8
RB8
Receive Shift Register
Read
SBUF
Internal
Data
Bus
Figure 22. Serial Port Mode 2
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
BAUD
CLOCK
FRAME
SIZE
START
BIT
STOP
BIT
9^TH BIT
FUNCTION
0
0
0
Synch. 4 or 12 TCLKs
8 bits
No
No
None
0
1
1
Asynch. Timer 1 or 2
10 bits
1
1
None
1
0
2
Asynch. 32 or 64 TCLKs 11 bits
1
1
0, 1
1
1
3
Asynch. Timer 1 or 2
11 bits
1
1
0, 1
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