Renesas M16C Series User Manual page 49

M30245 Group
The clock-synchronous serial I/O has three types of CTS/RTS functions to choose from:
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• CTS/RTS functions disabled
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• CTS function only enabled
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• RTS function only enabled
(b) Function for choosing CLK polarity
This function switches the polarity of the transfer clock. The following operations are available:
• Data is input at the falling edge of the transfer clock, and is output at the rising edge.
• Data is input at the rising edge of the transfer clock, and is output at the falling edge.
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(c) Function for choosing which bit to transmit/receive first
This function is to choose whether to transmit/receive data from bit 0 or from bit 7. Choose either of
the following:
• LSB first
• MSB first
(d) Function for choosing continuous receive mode
Continuous receive mode is a mode in which reading the receive buffer register makes the reception-
enabled status ready. In this mode, there is no need to write dummy data to the transmit buffer
register so as to make the reception-enabled status ready. But at the time of starting reception, read
the receive buffer register into a dummy manner.
• Normal mode
• Continuous receive mode
(e) Data logic select function
This function is to reverse data when writing to transmit buffer register or reading from receive buffer register.
(f) Function for choosing a transmission interrupt factor
The timing to generate a transmission interrupt can be selected from the following: the instant the
transmission buffer is emptied or the instant the transmission register is emptied. When transmis-
sion buffer empty timing is selected, an interrupt occurs when transmitted data is moved from the
transmission buffer to the transmission register. Therefore, data can be transmitted in succession.
When transmission register empty timing is selected, an interrupt occurs when data transmission is
complete.
(g) TxD, RxD I/O polarity reverse function
This function is to reverse a polarity of TxD port output level and a polarity of RxD port input level.
Following are some examples in which various functions (a) through (g) are selected:
• Transmission Operation WITH: CTS function, transmission at falling edge of transfer clock, LSB
First, interrupt at instant transmission buffer is emptied
• Transmission Operation WITH: CTS/RTS function disabled, transmission at falling edge of transfer
clock, LSB First, interrupt at instant transmission is completed
• Reception Operation WITH: RTS function, reception at falling edge of transfer clock, LSB First, suc-
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Data is transmitted/receivec from bit 0.
Data is transmitted/received from bit 7.
Writing dummy data to the transmit buffer register makes the
reception enabled status ready.
Reading the reception buffer register makes the reception-enabled
status ready.
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CTS/RTS pin is a programmable I/O port.
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CTS/RTS pin performs the CTS function.
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CTS/RTS pin performs the RTS function.
2. Clock-Synchronous Serial I/O
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