Transmitting A Start Frame - Renesas RX100 Series User Manual

RX13T Group
23.10.2

Transmitting a Start Frame

Figure 23.60 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. Figure 23.61 and Figure 23.62 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.
Break Field low width
TXDX12 pin
STR.BFDF
(1)
The above diagram assumes the following:
ESMER: ESME = 1
PCR: TXDXPS = 0
ICR: BFDIE = 1
TMR: TOMS[1:0] = 10b
Figure 23.60 Example of Operations When Transmitting a Start Frame
R01UH0822EJ0100 Rev.1.00
Jul 31, 2019
Start Frame
Control Field 0
8 bits
Write 1 to
STCR.BFDCL
(2) (3)
23. Serial Communications Interface (SCIg, SCIh)
Control Field 1
8 bits
(4)
Information Frame
Data Field
(5)
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