NEC mPD780024AS Series Preliminary User's Manual page 229

(b) Parity types and operations
The parity bit is used to detect bit errors in communication 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 that includes a parity bit is controlled so that there are an even
number of bits whose value is 1. The value of the parity bit is as follows.
If the transmit data contains an odd number of bits whose value is 1: the parity bit is "1"
If the transmit data contains an even number of bits whose value is 1: the parity bit is "0"
• During reception
The number of bits whose value is 1 is counted among the receive data that include a parity bit, and
a parity error occurs when the counted result is an odd number.
(ii) Odd parity
• During transmission
The number of bits in transmit data that includes a parity bit is controlled so that there is an odd number
of bits whose value is 1. The value of the parity bit is as follows.
If the transmit data contains an odd number of bits whose value is 1: the parity bit is "0"
If the transmit data contains an even number of bits whose value is 1: the parity bit is "1"
• During reception
The number of bits whose value is 1 is counted among the receive data that include a parity bit, and
a parity error occurs when the counted 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.
CHAPTER 13 SERIAL INTERFACE (UART0)
Preliminary User's Manual U16035EJ1V0UM
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