PixArt Imaging Inc.

PAC107

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39

PixArt Imaging Inc.

E-mail:

fae_service@pixart.com.tw

V1.4, Aug, 2005

register. As eight shifts at S6P2 of every peripheral cycle, the LSB (D7) is done, then

hardware asserts RI (S1P1) to indicate reception completed. Software can read the received

byte from SBUF.

Asynchronous Modes (Modes 1, 2, and 3)

Mode 1

Mode 1 is a full-duplex, asynchronous mode. The data frame consists of 10 bits. They are

one start bit, 8 data bits, and one stop bit. Serial data is transmitted via TXD pin and

received through RXD pin. When a data frame is received, the stop bit is read from RB8 bit

in SCON. The baud rate is generated by overflow of Timer 1 or Timer 2.

Mode 2 and Mode 3

Modes 2 and 3 are full-duplex, asynchronous modes. There are 11 bits per transfer frame.

They are one start bit, 8 data bits (LSB first), one programmable 9

bit is read from the RB8 bit in the SCON register. When transmit, the 9

to TB8 bit in SCON. The 9

- In mode 2, the baud rate is programmable to 1/32 or 1/64 of the oscillator frequency.

- In mode 3, the baud rate is generated by overflow of timer 1 or timer 2.

Transmission (Modes 1, 2, 3)

Follow these steps to initiate a transmission:

1. Write to the SCON register. Select the mode with the SM0 and SM1 bits, and clear the

REN bit. For modes 2 and 3, also write the ninth bit to the TB8 bit.

2. Write the byte to be transmitted to the SBUF register. This write stars the transmission.

Reception (Modes 1, 2, 3)

To prepare for a reception, set the REN bit in the SCON register. The actual reception is

D0

D1

D2

D3

D4

D5

D6

D7

D8

Start Bit

Data Byte

Ninth Data Bit (Modes 2 and 3 only)

Stop Bit

Data Frame (Modes 1, 2, and 3)