AT89C5132 Atmel Corporation, AT89C5132 Datasheet - Page 112

• Manufacturer Part Number: AT89C5132
• Manufacturer: Atmel Corporation

Specifications of AT89C5132

• Flash (kbytes): 64 Kbytes
• Max. Operating Frequency: 20 MHz
• Cpu: 8051-12C
• Max I/o Pins: 44
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 1
• Uart: 1
• Adc Channels: 2
• Adc Resolution (bits): 10
• Adc Speed (ksps): 22.7
• Sram (kbytes): 2.25
• Self Program Memory: API
• Operating Voltage (vcc): 2.7 to 3.6
• Timers: 2
• Isp: UART/USB
• Watchdog: Yes

18.4.2
18.4.3
18.4.4
112
AT89C5132
Reception
(Modes 1, 2 and 3)
Framing Error Detection
(Modes 1, 2 and 3)
Baud Rate Selection (Modes 1 and 3)
To prepare for reception, write to SCON register, setting SM0 and SM1 Bits according to
Table 89, and set the REN bit. The actual reception is then initiated by a detected high-to-low
transition on the RXD pin.
Framing error detection is provided for the three asynchronous modes. To enable the framing bit
error detection feature, set SMOD0 bit in PCON register as shown in Figure 18-11.
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 devices. If a valid stop bit is not found, the software sets FE bit in SCON register.
Software may examine FE bit after each reception to check for data errors. Once set, only soft-
ware or a chip reset clears FE bit. Subsequently received frames with valid stop Bits cannot
clear FE bit. When the framing error detection feature is enabled, RI rises on stop bit instead of
the last data bit as detailed in Figure 18-17.
Figure 18-11. Framing Error Block Diagram
In modes 1 and 3, the Baud Rate is derived either from the Timer 1 or the Internal Baud Rate
Generator and allows different baud rate in reception and transmission.
As shown in Figure 18-12, the selection is done using RBCK and TBCK Bits in BDRCON
register.
Figure 18-13 gives the baud rate calculation formulas for each baud rate source. Table 90
details Internal Baud Rate Generator configuration for different peripheral clock frequencies and
gives baud rates closer to the standard baud rates.
Figure 18-12. Baud Rate Source Selection (Modes 1 and 3)
CLOCK
CLOCK
IBRG
T1
BDRCON.2
RBCK
Framing Error
0
1
Controller
÷ 16
FE
To Serial
Rx Port
SM0
SMOD0
PCON.6
CLOCK
CLOCK
1
0
IBRG
T1
SM0/FE
BDRCON.3
SCON.7
TBCK
0
1
÷ 16
4173E–USB–09/07
To Serial
Tx Port