Control And Data Port Communications; Word Length And Parity - PictureTel Concorde 4500 Servicing Manual

Word Length and
Parity
Control and Data Port
This appendix describes some background information necessary
for understanding data communications.
Word length refers to the number of bits that make up one word of
data. A word is usually 7 or 8 bits and includes the bits between the
start bit and the stop bit.
Parity is an error detection scheme in which the transmitter and
receiver are set to expect all incoming words to have an even or odd
number of bits set to binary one.
For example, suppose that the Concorde¥4500 and the peripheral
device are set for odd parity. The sender looks at the word to be
transmitted, and if it has an even number of ones, the sender sets the
Þnal bit in the word (the parity bit) to one so that the word will have
an odd number of ones. The receiver counts the number of ones in
the incoming word, including the parity bit. If there is an even
number of ones, the receiver logs an error.
The following Þgure illustrates the stop bits and the parity bits (P)
in some asynchronous data format examples.
This document was created with FrameMaker 4.0.4
Communications
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