UPD78F0411GA-GAM-AX Datasheet, PDF (362/564 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

CHAPTER 14 SERIAL INTERFACE UART6
(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 register 6 (ASIF6) is 00H before writing transmit data to transmit buffer register 6
(TXB6).
TXBF6
0
1
Writing enabled
Writing disabled
Writing to TXB6 Register
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
0
1
Transmission Status
Transmission is completed.
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.
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User’s Manual U18698EJ1V0UD