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Q52196: Serial Communications Parity Definition

Article: Q52196
Product(s): Microsoft Disk Operating System
Version(s): MS-DOS:3.x,4.x,5.x,6.0,6.2,6.21,6.22
Operating System(s): 
Keyword(s): 
Last Modified: 17-DEC-2000

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The information in this article applies to:

- Microsoft MS-DOS operating system versions 3.1, 3.2, 3.21, 3.3, 3.3a, 4.0, 4.01, 5.0, 5.0a, 6.0, 6.2, 6.21, 6.22 
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SUMMARY
=======

In serial communications, the parity bit is used in a simple error detection
algorithm. As a stream of data bits is formed, an extra bit, called the parity
bit, is added. This bit is set on (1) or off (0), depending on the serial
communications parameters set in the UART chip. The following table lists the
available parity parameters and their meanings:

  Parameter  Meaning
  ---------  -------

  ODD        Parity bit set so that there is an odd number of 1 bits
  EVEN       Parity bit set so that there is an even number of 1 bits
  NONE       Parity bit is ignored, value is indeterminate
  MARK       Parity bit is ALWAYS set to 1
  SPACE      Parity bit is ALWAYS set to 0

MORE INFORMATION
================

For the ASCII characters "G" (0x47) and "I" (0x049), the binary equivalents are
00100111 and 00101001. The following table is an example of how a parity bit
would be coded for these values (the last bit is used as the parity bit):

             G             I

  ODD   - 001001111     001010010
  EVEN  - 001001110     001010011
  NONE  - 00100111?     00101001?
  MARK  - 001001111     001010011
  SPACE - 001001110     001010010


Additional query words: 6.22 3.20 3.21 3.30 3.30a 4.00 4.01 5.00 5.00a 6.00 6.20

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Keywords          :  
Technology        : kbMSDOSSearch kbMSDOS321 kbMSDOS400 kbMSDOS320 kbMSDOS330a kbMSDOS621 kbMSDOS622 kbMSDOS620 kbMSDOS600 kbMSDOS310 kbMSDOS500 kbMSDOS330 kbMSDOS401 kbMSDOS500a
Version           : MS-DOS:3.x,4.x,5.x,6.0,6.2,6.21,6.22

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