
Philips Semiconductors
Product data
P8xC660X2/661X2
80C51 8-bit microcontroller family
16 KB OTP/ROM, 512B
RAM, low voltage (2.7 to 5.5 V), low power, high speed (30/33
MHz), two 400KB I
2
C interfaces
2003 Oct 02
26
80C51 Internal Bus
SBUF
Zero Detector
D S
CL
Write
to
SBUF
TX Control
TX Clock
Send
Data
Start
RX Control
Start
RX Clock RI
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
Timer 1
Overflow
SMOD = 1
SMOD = 0
Shift
Bit Detector
Transmit
Send
S1P1
Shift
TX
Clock
Write to SBUF
Start Bit
TxD
Stop Bit
D0
D1
D2
D3
D4
D5
D6
D7
TI
RxD
RX
Clock
÷
16 Reset
Start
Bit
RxD
Bit Detector
Sample Times
Stop Bit
D0
D1
D2
D3
D4
D5
D6
D7
Shift
RI
Receive
Data
÷
16
Load
SBUF
Shift
1FFH
SU00540
Figure 10. Serial Port Mode 1