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UM0404
Asynchronous / synchronous serial interface
S0RBUF (FEB2h / 59h)
SFR
Reset Value: 0xxxh
10.1 Asynchronous
operation
Asynchronous mode supports full-duplex communication, where both transmitter and
receiver use the same data frame format and the same Baud rate. Data is transmitted on pin
TXD0/P3.10 and received on pin RXD0/P3.11. These signals are alternate functions of
Port3 pins.
Figure 100. Asynchronous mode of serial channel ASC0
Asynchronous data frames
8-bit data frames
either consist of 8 data bits D7...D0 (S0M = ‘001b’), or of 7 data bits
D6...D0 plus an automatically generated parity bit (S0M = ‘011b’). Parity may be odd or
even, depending on bit S0ODD in register S0CON. An even parity bit will be set, if the
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
-
-
-
-
-
-
-
Received Data
RW
2
CPU
Clock
S0R
Baud Rate Timer
Reload Register
16
Clock
Serial Port Control
Shift Clock
S0M S0STP
S0FE
S0OE
S0PE
S0REN
S0FEN
S0PEN
S0OEN
S0LB
S0RIR
S0TIR
S0EIR
Receive Interrupt
Request
Transmit Interrupt
Request
Error Interrupt
Request
Transmit Shift
Register
Receive Shift
Register
TXD0 Output
Transmit Buffer
Register S0TBUF
Receive Buffer
Register S0RBUF
Sampling
MUX
0
1
RXD0 Input
Internal Bus
P3.10
P3.11