Renesas M16C FAMILY, Руководство пользователя

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Rev.2.00 Oct 16, 2006 page 45 of 354
REJ09B0340-0200
M30245 Group 2. Clock-Synchronous Serial I/O
In transmitting data in clock-synchronous serial I/O mode, choose functions from those listed in Table
2.3.1. Operations of the circled items are described below. Figure 2.3.5 shows the operation timing, and
Figures 2.3.6 and 2.3.7 show the set-up procedures.
2.3.2 Operation of Serial I/O (transmission in clock-synchronous serial I/O mode)
(1) Setting the transmit enable bit to “1” and writing transmission data to the UARTi transmit
buffer register makes data transmissible status ready.
________ _______
(2) When input to the CTSi pin goes to “L” level, transmission starts (the CTSi pin must be
controlled on the reception side).
(3) In synchronization with the first falling edge of the transfer clock, transmission data held in the
UARTi transmit buffer register is transmitted to the UARTi transmit register. At this time, the
UARTi transmit interrupt request bit goes to “1”. Also, the first bit of the transmission data is
transmitted from the TxDi pin. Then the data is transmitted bit by bit from the lower order in
synchronization with the falling edges.
(4) When transmission of 1-byte data is completed, the transmit register empty flag goes to “1”,
which indicates that transmission is completed. The transfer clock stops at “H” level.
(5) If the next transmission data is set in the UARTi transmit buffer register while transmission is
in progress (before the eighth bit has been transmitted), the data is transmitted in succession.
Operation
Item Item Set-up Set-up
Transfer clock
source
CLK polarity
Internal clock (f
1
/ f
8
/ f
32
)
External clock (CLKi pin)
CTS function CTS function enabled
CTS function disabled
Output transmission data at
the falling edge of the
transfer clock
Output transmission data at
the rising edge of the
transfer clock
O
O
O
Transmission
interrupt factor Transmission buffer empty
Transmission complete
O
Transfer clock LSB first
MSB first
O
Data logic select
function
No reverse
Reverse
O
T
X
D, R
X
D I/O
polarity reverse bit
No reverse
Reverse
O
Table 2.3.1. Choosed functions