TS80C54 ATMEL [ATMEL Corporation], TS80C54 Datasheet - Page 19

• Manufacturer Part Number: TS80C54
• Description: 8-bit CMOS Microcontroller 16/32 Kbytes ROM/OTP
• Manufacturer: ATMEL [ATMEL Corporation]

9. TS80C54/58X2 Serial I/O Port
9.1
4431E–8051–04/06
Framing Error Detection
SMOD0=X
The serial I/O port in the TS80C54/58X2 is compatible with the serial I/O port in the 80C52.
It provides both synchronous and asynchronous communication modes. It operates as an Uni-
versal Asynchronous Receiver and Transmitter (UART) in three full-duplex modes (Modes 1, 2
and 3). Asynchronous transmission and reception can occur simultaneously and at different
baud rates
Serial I/O port includes the following enhancements:
Framing bit error detection is provided for the three asynchronous modes (modes 1, 2 and 3). To
enable the framing bit error detection feature, set SMOD0 bit in PCON register (See Figure 9-1).
Figure 9-1.
When this feature is enabled, the receiver checks each incoming data frame for a valid stop bit.
An invalid stop bit may result from noise on the serial lines or from simultaneous transmission by
two CPUs. If a valid stop bit is not found, the Framing Error bit (FE) in SCON register (See Table
9-3.) bit is set.
Software may examine FE bit after each reception to check for data errors. Once set, only soft-
ware or a reset can clear FE bit. Subsequently received frames with valid stop bits cannot clear
FE bit. When FE feature is enabled, RI rises on stop bit instead of the last data bit (See Figure 9-
2. and Figure 9-3.).
Figure 9-2.
SMOD0=1
• Framing error detection
• Automatic address recognition
SM0/FE
SMOD1
RXD
FE
RI
SMOD0
SM1
Framing Error Block Diagram
UART Timings in Mode 1
Start
bit
SM2
-
D0
REN
Set FE bit if stop bit is 0 (framing error) (SMOD0 = 1)
SM0 to UART mode control (SMOD = 0)
POF
To UART framing error control
D1
TB8
GF1
D2
RB8
GF0
D3
Data byte
D4
PD
TI
D5
IDL
RI
D6
SCON (98h)
PCON (87h)
D7
Stop
bit
AT/TS8xC54/8X2
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