W77C32_07 Datasheet, PDF (63/78 Pages) Winbond – 8-BIT MICROCONTROLLER

W77C32/W77C032A
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 ^SOUT
LOAD
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 W77C032 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 W77C032 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
set to 1, then the FE flag is indicated in SM0/FE. When SMOD0 is set to 0, then the SM0 flag is
indicated in SM0/FE.
The FE bit is set to 1 by hardware but must be cleared by software. Note that SMOD0 must be 1 while
reading or writing to FE or FE_1. If FE is set, then any following frames received without any error will
not clear the FE flag. The clearing has to be done by software.
Multiprocessor Communications
Multiprocessor communications makes use of the 9^th data bit in modes 2 and 3. In the W77C032, the
RI flag is set only if the received byte corresponds to the Given or Broadcast address. This hardware
feature eliminates the software overhead required in checking every received address, and greatly
simplifies the software programmer task.
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Publication Release Date: February 1, 2007
Revision A8