AT80SND1C-ROTIL datasheet(136/210 Pages) ATMEL

136 / 210 page

136

AT8xC51SND1C

4109E–8051–06/03

Figure 97. Transmission Waveforms (Mode 0)

Reception (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)

Baud Rate Selection (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 SBUF

TXD

RXD

Write to SCON

TXD

RXD

Set REN, Clear RI

M0SRC

BDRCON.0

PER

CLOCK

÷ 6

To Serial Port

IBRG

CLOCK

Baud_Rate=

(1-SPD)

⋅ 32 ⋅ (256 -BRL)

SMOD1

⋅ F

PER

BRL= 256

(1-SPD)

⋅ 32 ⋅ Baud_Rate

SMOD1

⋅ F

PER

a. Fixed Formula

b. Variable Formula

Baud_Rate

FPER

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