Renesas M16C FAMILY, User Manual

Page: 51 / 369

Rev.2.00 Oct 16, 2006 page 40 of 354
REJ09B0340-0200
M30245 Group 2. Clock-Synchronous Serial I/O
_______ _______
The clock-synchronous serial I/O has three types of CTS/RTS functions to choose from:
_______ _______
• CTS/RTS functions disabled
_______ _______
CTS/RTS pin is a programmable I/O port.
_______
• CTS function only enabled
_______ _______ _______
CTS/RTS pin performs the CTS function.
_______
• RTS function only enabled
_______ _______ _______
CTS/RTS pin performs the RTS function.
(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.
(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 Data is transmitted/receivec from bit 0.
• MSB first Data is transmitted/received from bit 7.
(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 Writing dummy data to the transmit buffer register makes the
reception enabled status ready.
• Continuous receive mode Reading the reception buffer register makes the reception-enabled
status ready.
(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-