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CHAPTER 14 SERIAL INTERFACE 20
User’s Manual U14800EJ3V0UD
209
(b)
Parity types and operation
The parity bit is used to detect a bit error in the communication data. Normally, the same kind of parity
bit is used on the transmitting side and the receiving side. With even parity and odd parity, a one-bit
(odd number) error can be detected. With 0 parity and no parity, an error cannot be detected.
(i)
Even parity
At transmission
The transmission operation is controlled so that the number of bits with a value of 1 in the
transmit data including parity bit may be even. The parity bit value should be as follows.
The number of bits with a value of 1 is an odd number in transmit data:
1
The number of bits with a value of 1 is an even number in transmit data: 0
At reception
The number of bits with a value of 1 in the receive data including parity bit is counted, and if the
number is odd, a parity error is generated.
(ii)
Odd parity
At transmission
Conversely to the even parity, the transmission operation is controlled so that the number of bits
with a value of 1 in the transmit data including parity bit may be odd. The parity bit value should
be as follows.
The number of bits with a value of 1 is an odd number in transmit data:
0
The number of bits with a value of 1 is an even number in transmit data: 1
At reception
The number of bits with a value of 1 in the receive data including parity bit is counted, and if the
number is even, a parity error is generated.
(iii) 0 Parity
When transmitting, the parity bit is set to 0 irrespective of the transmit data.
At reception, a parity bit check is not performed.
Therefore, a parity error is not generated,
irrespective of whether the parity bit is set to 0 or 1.
(iv) No parity
A parity bit is not added to the transmit data. At reception, data is received assuming that there is
no parity bit. Since there is no parity bit, a parity error is not generated.