AT83C51SND1C_03 ATMEL [ATMEL Corporation], AT83C51SND1C_03 Datasheet - Page 136

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

Reception (Mode 0)
Baud Rate Selection (Mode 0)
136
AT8xC51SND1C
Figure 97. Transmission Waveforms (Mode 0)
To start a reception in mode 0, write to SCON register clearing SM0, SM1 and RI bits
and setting the REN bit.
As shown in Figure 98, Clock is pulsed and the LSB (D0) is sampled on the RXD pin.
The D0 bit is then shifted into the shift register. After eight samplings, the MSB (D7) is
shifted into the shift register, and hardware asserts RI bit to indicate a completed recep-
tion. Software can then read the received Byte from SBUF register.
Figure 98. Reception Waveforms (Mode 0)
In mode 0, the baud rate can be either, fixed or variable.
As shown in Figure 99, the selection is done using M0SRC bit in BDRCON register.
Figure 100 gives the baud rate calculation formulas for each baud rate source.
Figure 99. Baud Rate Source Selection (mode 0)
Figure 100. Baud Rate Formulas (Mode 0)
Write to SCON
Write to SBUF
a. Fixed Formula
Baud_Rate
RXD
RXD
TXD
TXD
RI
TI
=
CLOCK
CLOCK
IBRG
PER
F
PER
6
Set REN, Clear RI
D0
D0
÷ 6
D1
D1
D2
D2
BDRCON.0
M0SRC
D3
D3
0
1
BRL= 256
D4
D4
Baud_Rate=
b. Variable Formula
D5
To Serial Port
D5
-
6
(1-SPD)
6
D6
D6
(1-SPD)
2
SMOD1
⋅
2
32
SMOD1
⋅
D7
D7
32
⋅
⋅
Baud_Rate
⋅
F
4109E–8051–06/03
⋅
(256 -BRL)
PER
F
PER