Philips Semiconductors
Preliminary specification
80C453/83C453/87C453
CMOS single-chip 8-bit microcontrollers
1996 Aug 15
3-318
SCON
Address = 98H
Reset Value = 0000 0000B
SM0/FE
7
SM1
6
SM2
5
REN
4
TB8
3
RB8
2
Tl
1
Rl
0
Bit Addressable
(SMOD0 = 0/1)*
Symbol
Function
FE
Framing Error bit. This bit is set by the receiver when an invalid stop bit is detected. The FE bit is not cleared by valid
frames but should be cleared by software. The SMOD0 bit must be set to enable access to the FE bit.
Serial Port Mode Bit 0, (SMOD0 must = 0 to access bit SM0)
Serial Port Mode Bit 1
SM0
SM1
Mode
Description
Baud Rate**
0
0
0
shift register
f
OSC
/12
0
1
1
8-bit UART
variable
1
0
2
9-bit UART
f
OSC
/64 or f
OSC
/32
1
1
3
9-bit UART
variable
Enables the Automatic Address Recognition feature in Modes 2 or 3. If SM2 = 1 then Rl will not be set unless the
received 9th data bit (RB8) is 1, indicating an address, and the received byte is a Given or Broadcast Address.
In Mode 1, if SM2 = 1 then Rl will not be activated unless a valid stop bit was received, and the received byte is a
Given or Broadcast Address. In Mode 0, SM2 should be 0.
Enables serial reception. Set by software to enable reception. Clear by software to disable reception.
The 9th data bit that will be transmitted in Modes 2 and 3. Set or clear by software as desired.
In modes 2 and 3, the 9th data bit that was received. In Mode 1, if SM2 = 0, RB8 is the stop bit that was received.
In Mode 0, RB8 is not used.
Transmit interrupt flag. Set by hardware at the end of the 8th bit time in Mode 0, or at the beginning of the stop bit in the
other modes, in any serial transmission. Must be cleared by software.
Receive interrupt flag. Set by hardware at the end of the 8th bit time in Mode 0, or halfway through the stop bit time in
the other modes, in any serial reception (except see SM2). Must be cleared by software.
SM0
SM1
SM2
REN
TB8
RB8
Tl
Rl
NOTE:
*SMOD0 is located at PCON6.
**f
OSC
= oscillator frequency
SU00043
Bit:
Figure 5. Serial Port Control Register (SCON)
SMOD1
SMOD0
OSF
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 6. UART Framing Error Detection