W77C58 Datasheet, PDF (59/71 Pages) Winbond – 8 BIT MICROCONTROLLER

Preliminary W77C58
Table 10. Serial Ports Modes
SM1 SM0 MODE TYPE
BAUD CLOCK
00
01
10
11
0
Synch. 4 or 12 TCLKs
1 Asynch. Timer 1 or 2
2
Asynch. 32 or 64 T^CLKs
3 Asynch. Timer 1 or 2
FRAME
SIZE
8 bits
10 bits
11 bits
11 bits
START
BIT
No
1
1
1
STOP
BIT
No
1
1
1
9TH BIT
FUNCTION
None
None
0, 1
0, 1
Timer 1
Overflow
Timer 2 Overflow
(for Serial Port 0 only)
÷2
Write to
SBUF
TB8
Internal
Data Bus
SMOD=
(SMOD_1) ⁰
1
TCLK _{0 1}
÷16
TX START TX SHIFT
TX CLOCK
TI
RCLK
01
÷16
SAMPLE
1-TO-0
DETECTOR
SERIAL
CONTROLLER ^RI
RX CLOCK
RX
START
LOAD
SBUF
RX SHIFT
STOP
D8
PARIN
START
LOAD
SOUT
CLOCK
Transmit Shift Register
TXD
Serial Port
Interrupt
Read
SBUF
RXD
BIT
DETECTOR
CLOCK
PAROUT
SBUF
SIN
D8
RB8
Receive Shift Register
Internal
Data
Bus
Figure 23: Serial Port Mode 3
Framing Error Detection
A Frame Error occurs when a valid stop bit is not detected. This could indicate incorrect serial data
communication. Typically the frame error is due to noise and contention on the serial communication
line. The W77C58 has the facility to detect such framing errors and set a flag which can be checked
by software.
The Frame Error FE(FE_1) bit is located in SCON.7(SCON1.7). This bit is normally used as SM0 in
the standard 8051 family. However, in the W77C58 it serves a dual function and is called SM0/FE
(SM0_1/FE_1). There are actually two separate flags, one for SM0 and the other for FE. The flag that
is actually accessed as SCON.7(SCON1.7) is determined by SMOD0 (PCON.6) bit. When SMOD0 is
- 59 -
Publication Release Date: September 1999
Revision A1