upd70f3402 Renesas Electronics Corporation., upd70f3402 Datasheet - Page 418

• Manufacturer Part Number: upd70f3402
• Description: 32-/16-bit Single-chip Microcontroller With Can Interface
• Manufacturer: Renesas Electronics Corporation.

12.5.3 Procedure of continuous transmission
With UARTA, the next transmit data can be written to the UAnTX register as soon as the UARTAn trans-
mit shift register has started its shift operation. The timing at which data is transferred to the UARTAn
transmit shift register can be identified by the transmission enable interrupt request signal (INTUAnT).
The INTUAnT signal enables continuous transmission even while an interrupt is being serviced after
transmission of 1 data frame, so that an efficient communication rate can be realized.
During continuous transmission, do not write the next transmit data to the UAnTX register before a
transmit request interrupt signal (INTUAnT) is generated after transmit data is written to the UAnTX reg-
ister and transferred to the UARTAn transmit shift register. If a value is written to the UAnTX register
before a transmit request interrupt signal is generated, the previously set transmit data is overwritten by
the latest transmit data.
Caution:
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Continuous transmission operating (UAnTSF bit is 1), can not change register. While
continuous transmission is being executed, execute initialization after checking that
the UAnTSF bit is 0. If initialization is executed while the UAnTSF bit is 1, the transmit
data cannot be guaranteed.
Figure 12-11: Processing Flow of Continuous Transfer
Chapter 12 Asynchronous Serial Interface A (UARTA)
User’s Manual U16702EE3V2UD00
Transmission interrupt
Necessary number
of data written?
Write UAnTX.
Set registers.
occurred?
Start
End
Yes
Yes
No
No