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(b) Parity types and operations
The parity bit is used to detect bit errors in transfer data. Usually, the same type of parity bit is used by the
transmitting and receiving sides. When odd parity or even parity is set, errors in the parity bit (the odd-
number bit) can be detected. When zero parity or no parity is set, errors are not detected.
(i)
Even parity
•
During transmission
The number of bits in transmit data including the parity bit is controlled so that an even number of
"1" bits is set. The value of the parity bit is as follows.
If the transmit data contains an odd number of "1" bits: The parity bit value is "1"
If the transmit data contains an even number of "1" bits: The parity bit value is "0"
•
During reception
The number of "1" bits is counted among the receive data including a parity bit, and a parity error
occurs when the result is an odd number.
(ii)
Odd parity
•
During transmission
The number of bits in transmit data including a parity bit is controlled so that an odd number of "1"
bits is set. The value of the parity bit is as follows.
If the transmit data contains an odd number of "1" bits: The parity bit value is "0"
If the transmit data contains an even number of "1" bits: The parity bit value is "1"
•
During reception
The number of "1" bits is counted among the receive data including a parity bit, and a parity error
occurs when the result is an even number.
(iii) Zero parity
During transmission, the parity bit is set to "0" regardless of the transmit data.
During reception, the parity bit is not checked. Therefore, no parity errors will occur regardless of
whether the parity bit is a "0" or a "1".
(iv) No parity
No parity bit is added to the transmit data.
During reception, receive data is regarded as having no parity bit. Since there is no parity bit, no parity
errors will occur.
414
CHAPTER 10
SERIAL INTERFACE FUNCTION
User's Manual U13850EJ6V0UD
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