Rainbow-electronics AT89C5132 Manual de usuario descargar pdf (Pagina 109)

109

AT8xC5132

4173A–8051–08/02

Figure 79. 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 80, 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 sampling, 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 80. 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 81, the selection is done using M0SRC bit in BDRCON register.

Figure 82 gives the baud rate calculation formulas for each baud rate source.

Figure 81. Baud Rate Source Selection (mode 0)

Figure 82. Baud Rate Formulas (Mode 0)

Write to SBUF

TXD

RXD

D0 D1 D2 D3 D4 D5 D6 D7

Write to SCON

TXD

RXD

D0 D1 D2 D3 D4 D5 D6 D7

Set REN, Clear RI

M0SRC

BDRCON.0

PER

CLOCK

÷ 6

IBRG

CLOCK

Serial Port

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 =

PER

1 2 ... 104 105 106 107 108 109 110 111 112 113 114 ... 161 162

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Rainbow-electronics AT89C5132 Manual de usuario Pagina 109

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