Datasheet

Philips Semiconductors Product data
P80C3xX2; P80C5xX2;
P87C5xX2
80C51 8-bit microcontroller family
4K/8K/16K/32K ROM/OTP, low voltage (2.7 to 5.5 V),
low power, high speed (30/33 MHz)
2003 Jan 24
28
80C51 Internal Bus
SBUF
Zero Detector
D Q
S
CL
Write
to
SBUF
TX Control
TX Clock Send
Data
Start
RX Control
Start
Load
SBUF
RX Clock
T1
Serial
Port
Interrupt
Input Shift Register
(9 Bits)
Load
SBUF
Shift
SBUF
Read
SBUF
80C51 Internal Bus
TxD
TB8
÷ 16
1-to-0
Transition
Detector
Sample
÷ 2
SMOD = 1
SMOD = 0
Shift
Bit Detector
RxD
Stop Bit
Gen.
Mode 2
Phase 2 Clock
(1/2 f
OSC
in
12-clock mode;
f
OSC
in 6-clock
mode)
R1
÷ 16
Shift
1FFH
Transmit
Send
S1P1
Shift
TX
Clock
Write to SBUF
Start Bit
TxD
Stop BitD0 D1 D2 D3 D4 D5 D6 D7
TI
RX
Clock
÷ 16 Reset
Start
Bit
RxD
Stop BitD0 D1 D2 D3 D4 D5 D6 D7
Bit Detector
Sample Times
Shift
RI
Receive
Data
(SMOD is
PCON.7)
TB8
RB8
Stop Bit Gen.
SU01627
Figure 16. Serial Port Mode 2