R01UH0823EJ0100 Rev.1.00
Page 1077 of 1823
Jul 31, 2019
RX23W Group
33. Serial Communications Interface (SCIg, SCIh)
33.10.2
Transmitting a Start Frame
shows an example of operations to transmit a Start Frame, which is composed of the Break Field low
width, Control Field 0, and Control Field 1.
are flowcharts for the transmission of a
Start Frame.
Operations when the extended serial mode control section is to be used to transmit a Start Frame are as listed below. Be
sure to use the SCI12 in asynchronous mode.
(1) With Break Field low width output mode as the operating mode for the timer, writing 1 to the TCR.TCST bit starts
counting by the timer, and the low level will be output from the TXDX12 pin over the period corresponding to
registers TCNT and TPRE settings.
(2) The output on the TXDX12 pin is inverted when the timer counter underflows, and the STR.BFDF flag is set to 1.
An SCIX0 interrupt is also generated if the value of the ICR.BFDIE bit is 1.
(3) Write 0 to the TCR.TCST bit to stop counting by the timer, and send the data for Control Field 0. After the Break
Field low width output, stop counting before the next underflow occurs.
(4) When the data for Control Field 0 have been transmitted, the data for Control Field 1 is transmitted.
(5) When the data for Control Field 1 have been transmitted, an Information Frame is transmitted.
Omit the Break Field and Control Field 0 to suit the structure of the Start Frame.
Figure 33.61
Example of Operations When Transmitting a Start Frame
Break Field low width
Control Field 0
Start Frame
Control Field 1
Data Field
Information Frame
8 bits
8 bits
Write 1 to
STCR.BFDCL
The above diagram assumes the following:
ESMER: ESME = 1
PCR:
TXDXPS = 0
ICR:
BFDIE = 1
TMR:
TOMS[1:0] = 10b
(1)
(2)
(3)
(4)
(5)
TXDX12 pin
STR.BFDF