AT89C5131A-M Atmel Corporation, AT89C5131A-M Datasheet - Page 69

• Manufacturer Part Number: AT89C5131A-M
• Manufacturer: Atmel Corporation

Specifications of AT89C5131A-M

• Flash (kbytes): 32 Kbytes
• Max. Operating Frequency: 48 MHz
• Cpu: 8051-12C
• Max I/o Pins: 34
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 1
• Twi (i2c): 1
• Uart: 1
• Sram (kbytes): 1.25
• Eeprom (bytes): 1024
• Self Program Memory: API
• Operating Voltage (vcc): 2.7 to 5.5
• Timers: 4
• Isp: UART/USB
• Watchdog: Yes

15. Serial I/O Port
15.1
4337K–USB–04/08
Framing Error Detection
The serial I/O port in the AT89C5130A/31A-M 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 15-
1).
Figure 15-1. Framing Error Block Diagram
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
15-1) 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
15-2
Figure 15-2. UART Timings in Mode 1
• Framing error detection
• Automatic address recognition
and
Figure
SMOD0 = X
SMOD0 = 1
RXD
15-3).
SM0/FE
FE
RI
SMOD1
SMOD0
SM1
Start
Bit
D0
SM2
-
D1
REN
Set FE Bit if Stop Bit is 0 (framing error) (SMOD0 = 1)
SM0 to UART Mode Control (SMOD0 = 0)
POF
To UART Framing Error Control
D2
TB8
GF1
D3
Data Byte
RB8
GF0
D4
AT89C5130A/31A-M
D5
PD
TI
D6
IDL
RI
D7
SCON (98h)
PCON (87h)
Stop
Bit
Figure
Table
69