W78E054D Datasheet, PDF (60/89 Pages) List of Unclassifed Manufacturers – 8-bit microcontroller

W78E054D/W78E052D Data Sheet
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 in-
volves 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
1/2
SMOD 0 1
0
1
TCLK
RCLK ⁰
1
1/16
1/16
SAMPLE
1-To-0
DETECTOR
Write to
SBUF
TX START
TX CLOCK
Transmit Shift Register
1
TB8
Internal
Data Bus
0
STOP
D8
PARIN
START ^SOUT
TXD
LOAD
CLOCK
TX SHIFT
Serial
Controllor ^TI
RX CLOCK
RI
Serial Interrupt
TX START
LOAD SBUF
RX SHIFT
Read SBUF
CLOCK PAROUT
SBUF
Internal
Data Bus
RXD
BIT
DETECTOR
SIN
D8
RB8
Receive Shift Register
Figure 16–4 Serial port mode 3
SM0 SM1 Mode
0
0
0
0
1
1
1
0
2
1
1
3
Type
Synch.
Asynch.
Asynch.
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
Table 16–5 Serial Ports Modes
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: Jun 9, 2015
Revision A13