
Philips Semiconductors
Product data
P87C51RA2/RB2/RC2/RD2
80C51 8-bit microcontroller family 8KB/16KB/32KB/64KB OTP
with 512B/1KB RAM, low voltage (2.7 to 5.5 V), low power, high
speed (30/33 MHz)
2003 Jan 24
29
SMOD1
SMOD0
–
POF
LVF
GF0
GF1
IDL
PCON
(87H)
SM0 / FE
SM1
SM2
REN
TB8
RB8
TI
RI
SCON
(98H)
D0
D1
D2
D3
D4
D5
D6
D7
D8
STOP
BIT
DATA BYTE
ONLY IN
MODE 2, 3
START
BIT
SET FE BIT IF STOP BIT IS 0 (FRAMING ERROR)
SM0 TO UART MODE CONTROL
0 : SCON.7 = SM0
1 : SCON.7 = FE
SU00044
Figure 13. UART Framing Error Detection
SM0
SM1
SM2
REN
TB8
RB8
TI
RI
SCON
(98H)
D0
D1
D2
D3
D4
D5
D6
D7
D8
1
0
COMPARATOR
11
X
RECEIVED ADDRESS D0 TO D7
PROGRAMMED ADDRESS
IN UART MODE 2 OR MODE 3 AND SM2 = 1:
INTERRUPT IF REN=1, RB8=1 AND “RECEIVED ADDRESS” = “PROGRAMMED ADDRESS”
– WHEN OWN ADDRESS RECEIVED, CLEAR SM2 TO RECEIVE DATA BYTES
– WHEN ALL DATA BYTES HAVE BEEN RECEIVED: SET SM2 TO WAIT FOR NEXT ADDRESS.
SU00045
Figure 14. UART Multiprocessor Communication, Automatic Address Recognition