AT83C51SND1C_03 ATMEL [ATMEL Corporation], AT83C51SND1C_03 Datasheet - Page 138

• Manufacturer Part Number: AT83C51SND1C_03
• Description: Single-Chip Flash Microcontroller with MP3 Decoder and Human Interface
• Manufacturer: ATMEL [ATMEL Corporation]

Framing Error Detection
(Modes 1, 2 and 3)
Baud Rate Selection (Modes 1
and 3)
138
AT8xC51SND1C
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 104.
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 2 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 software or a chip reset clear 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 110.
Figure 104. 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 105 the selection is done using RBCK and TBCK bits in BDRCON
register.
Figure 106 gives the baud rate calculation formulas for each baud rate source while
Table 124 details Internal Baud Rate Generator configuration for different peripheral
clock frequencies and giving baud rates closer to the standard baud rates.
Figure 105. Baud Rate Source Selection (Modes 1 and 3)
Figure 106. Baud Rate Formulas (Modes 1 and 3)
CLOCK
CLOCK
IBRG
Baud_Rate=
BRL= 256 -
T1
a. IBRG Formula
BDRCON.2
6
6
RBCK
(1-SPD)
(1-SPD)
0
1
2
2
SMOD1
SMOD1
⋅ 32 ⋅ Baud_Rate
⋅ 32 ⋅ (256 -BRL)
Framing Error
Controller
⋅ F
⋅ F
÷ 16
PER
PER
To Serial
Rx Port
FE
SM0
CLOCK
CLOCK
IBRG
SMOD0
PCON.6
T1
1
0
Baud_Rate=
BDRCON.3
TH1= 256 -
TBCK
SM0/FE
0
1
SCON.7
b. T1 Formula
6 Þ 32 Þ (256 -TH1)
192 ⋅ Baud_Rate
÷ 16
2
2
SMOD1
SMOD1
4109E–8051–06/03
⋅ F
⋅ F
PER
PER
To Serial
Tx Port