7477 datasheet(137/361 Pages) RENESAS

137 / 361 page

7470/7471/7477/7478 GROUP USER’S MANUAL

1-130

HARDWARE

1.13 Serial I/O

(8) Processing upon occurrence of errors

2 When a parity error, a framing error or a summing error occurs

When a parity error, a framing error or a summing error occurs, the flag corresponding to each

error in the Serial I/O status register is set to “1.” These flags are not cleared to “0” automatically.

Clear them to “0” by software.

The parity error flag, the framing error flag and the summing error flag can be cleared to “0” by

one of the following two methods.

q Clear the receive enable bit to “0.”

q Write arbitrary dummy data into the Serial I/O status register.

2 Processing upon occurrence of overrun error

An overrun error occurs when data has all been input to the Receive shift register while data is

stored in the Receive buffer register.

When an overrun error occurs, the data of the Receive shift register is not transferred to the

Receive buffer register and the data of the Receive buffer register is held. At this time, even if

the data of the Receive buffer register is read out, the data of the Receive shift register is not

transferred. Accordingly, the data of the Receive buffer register can be read out but the data of

the Receive shift register cannot be read out and becomes invalid.

When an overrun error occurs, clear the overrun error flag of the Serial I/O status register to “0”

and then make preparations for receiving data again.

The overrun error flag can be cleared by one of the following methods.

q Clear the serial I/O enable bit to “0.”

q Clear the receive enable bit to “0.”

q Write arbitrary dummy data into the Serial I/O status register.

7477 Datasheet(PDF) 137 Page - Renesas Technology Corp