Datasheet

78K0/Kx2-L CHAPTER 14 SERIAL INTERFACE UART6

R01UH0028EJ0400 Rev.4.00 472

Sep 27, 2010

(d) Continuous transmission

The next transmit data can be written to transmit buffer register 6 (TXB6) as soon as transmit shift register 6

(TXS6) has started its shift operation. Consequently, even while the INTST6 interrupt is being serviced after

transmission of one data frame, data can be continuously transmitted and an efficient communication rate can be

realized. In addition, the TXB6 register can be efficiently written twice (2 bytes) without having to wait for the

transmission time of one data frame, by reading bit 0 (TXSF6) of asynchronous serial interface transmission

status register 6 (ASIF6) when the transmission completion interrupt has occurred.

To transmit data continuously, be sure to reference the ASIF6 register to check the transmission status and

whether the TXB6 register can be written, and then write the data.

Cautions 1. The TXBF6 and TXSF6 flags of the ASIF6 register change from “10” to “11”, and to “01”

during continuous transmission. To check the status, therefore, do not use a combination

of the TXBF6 and TXSF6 flags for judgment. Read only the TXBF6 flag when executing

continuous transmission.

2. When the device is use in LIN communication operation, the continuous transmission

function cannot be used. Make sure that asynchronous serial interface transmission status

TXBF6 Writing to TXB6 Register

0 Writing enabled

1 Writing disabled

Caution To transmit data continuously, write the first transmit data (first byte) to the TXB6 register. Be

sure to check that the TXBF6 flag is “0”. If so, write the next transmit data (second byte) to the

TXB6 register. If data is written to the TXB6 register while the TXBF6 flag is “1”, the transmit

data cannot be guaranteed.

The communication status can be checked using the TXSF6 flag.

TXSF6 Transmission Status

0 Transmission is completed.

1 Transmission is in progress.

Cautions 1. To initialize the transmission unit upon completion of continuous transmission, be sure to

check that the TXSF6 flag is “0” after generation of the transmission completion interrupt,

and then execute initialization. If initialization is executed while the TXSF6 flag is “1”, the

transmit data cannot be guaranteed.

2. During continuous transmission, the next transmission may complete before execution of

INTST6 interrupt servicing after transmission of one data frame. As a countermeasure,

detection can be performed by developing a program that can count the number of transmit

data and by referencing the TXSF6 flag.