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STR71x UART COMMUNICATION WITH A PC USING RS232

1 SERIAL COMMUNICATION

The main features of the serial communication are summarized below.

1.1 MAIN FEATURES

The serial interface described here, allows two digital systems to communicate using only a

few wires. It is asynchronous, so it doesn’t need a clock.

The serial interface requires at least two wires:

– a transmitter wire (Tx)

– a receiver wire (Rx)

The interface is full-duplex, i.e. it can transmit and receive at the same time.

Figure 1. STR71x and UART interface Setup

1.2 BAUD RATES

Transmission and reception are driven by a baud rate generator. However, be aware that to

communicate correctly, the receiver must have exactly the same baud rate as the transmitter

baud rate, otherwise the communication will be corrupted. If this condition is met, a wide range

of baudrates is possible.

1.3 FRAMES

Communication frames begin with a start bit and end with a stop bit. Stop bits can be 0.5, 1,

1.5 or 2 bits long. Frame words can be 8 or 9 bits long. The least significant bit is sent first (see

Figure 2). In 8-bit word mode, the eighth bit can be a data bit or a parity bit, but in 9-bit word

mode, the ninth bit is a parity bit. Parity can be odd or even. Receiver and transmitter devices

must have the same word length, the same parity and the same number of stop bits.

UART Tx

Rx

Tx

Rx

STR71x

DEVICE

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