Rainbow-electronics AT89C5132 Manual do Utilizador descarregar pdf (Página 110)

110

AT8xC5132

4173A–8051–08/02

Asynchronous Modes

(Modes 1, 2 and 3)

The Serial Port has one 8-bit and two 9-bit asynchronous modes of operation. Figure 83

shows the Serial Port block diagram in asynchronous modes.

Figure 83. Serial I/O Port Block Diagram (Modes 1, 2 and 3)

Mode 1 Mode 1 is a full-duplex, asynchronous mode. The data frame (see Figure 84) consists of

10 Bits: one start, eight data Bits and one stop bit. Serial data is transmitted on the TXD

pin and received on the RXD pin. When data is received, the stop bit is read in the RB8

bit in SCON register.

Figure 84. Data Frame Format (Mode 1)

Modes 2 and 3 Modes 2 and 3 are full-duplex, asynchronous modes. The data frame (see Figure 85)

consists of 11 Bits: one start bit, eight data Bits (transmitted and received LSB first), one

programmable ninth data bit and one stop bit. Serial data is transmitted on the TXD pin

and received on the RXD pin. On receive, the ninth bit is read from RB8 bit in SCON

tively, the ninth bit can be used as a command/data flag.

Figure 85. Data Frame Format (Modes 2 and 3)

Transmission (Modes 1, 2

and 3)

To initiate a transmission, write to SCON register, setting SM0 and SM1 Bits according

to Table 105, and setting the ninth bit by writing to TB8 bit. Then, writing the byte to be

transmitted to SBUF register starts the transmission.

Reception (Modes 1, 2 and 3) To prepare for reception, write to SCON register, setting SM0 and SM1 Bits according to

Table 105, and set the REN bit. The actual reception is then initiated by a detected high-

to-low transition on the RXD pin.

TB8

SCON.3

IBRG

CLOCK

RXD

TXDSBUF Tx SR

Rx SR

SM1

SCON.6

SM0

SCON.7

Mode Decoder

M3 M2 M1 M0

SCON.0

SCON.1

Mode & Clock

Controller

SBUF Rx RB8

SCON.2

SM2

SCON.4

CLOCK

PER

CLOCK

Mode 1 D0 D1 D2 D3 D4 D5 D6 D7

Start bit 8-bit data Stop bit

Modes 2 and 3 D0 D1 D2 D3 D4 D5 D6 D8

Start bit 9-bit data Stop bit

1 2 ... 105 106 107 108 109 110 111 112 113 114 115 ... 161 162

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