Black Box USB Single-Port Hub IC266A Specifikace stáhnout pdf (Strana 23)

USB SINGLE-PORT HUB (RS-422/485)

Appendix C. Asynchronous

Communications

Serial data communications implies that individual bits

of a character are transmitted consecutively to a receiver

that assembles the bits back into a character. Data rate,

error checking, handshaking, and character framing

(start/stop bits) are pre-defined and must correspond at

both the transmitting and receiving ends.

Asynchronous communications is the standard means of

serial data communication for PC compatibles and PS/2

computers. The original PC was equipped with a

communication or COM: port that was designed around

an 8250 Universal Asynchronous Receiver Transmitter

(UART). This device allows asynchronous serial data to

be transferred through a simple and straightforward

programming interface. Character boundaries for

asynchronous communications are defined by a starting

bit followed by a pre-defined number of data bits (5, 6,

7, or 8). The end of the character is defined by the

transmission of a pre-defined number of stop bits

(usually 1, 1.5, or 2). An extra bit used for error

detection is often appended before the stop bits.

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Black Box USB Single-Port Hub IC266A Specifikace Strana 23