Renesas M16C FAMILY, User Manual

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Rev.2.00 Oct 16, 2006 page 64 of 354
REJ09B0340-0200
M30245 Group 2. UART
In transmitting data in UART mode, choose functions from those listed in Table 2.4.4. Operations of the
circled items are described below. Figure 2.4.7 shows the operation timing, and Figures 2.4.8 and 2.4.9
show the set-up procedures.
2.4.2 Operation of Serial I/O (transmission in UART mode)
Item Set-up
Transfer clock
source
Internal clock (f
1
/ f
8
/ f
32
)
External clock (CLKi pin)
CTS function CTS function enabled
CTS function disabled
O
O
Transmission
interrupt factor
Transmission buffer empty
Transmission complete O
Item Set-up
Data logic select
function
No reverse
Reverse
O
T
X
D, R
X
D I/O
polarity reverse bit
No reverse
Reverse
O
Bus collision
detection function
O
Not selected
Selected
Table 2.4.4. Choosed functions
(1) Setting the transmit enable bit to “1” and writing transmission data to the UARTi transmit
buffer register readies the data transmissible status.
________ ________
(2) When input to the CTSi pin goes to “L”, transmission starts (the CTSi pin needs to be con-
trolled on the reception side).
(3) Transmission data held in the UARTi transmit buffer register is transmitted to the UARTi
transmit register. At this time, the first bit (the start bit) of the transmission data is transmitted
from the TxDi pin. Then, data is transmitted, bit by bit, in sequence: LSB, ····, MSB, parity bit,
and stop bit(s).
(4) When the stop bit(s) is (are) transmitted, the transmit register empty flag goes to “1”, which
indicates that transmission is completed. At this time, the UARTi transmit interrupt request bit
goes to “1”. The transfer clock stops at “H” level.
(5) If the transmission condition of the next data is ready when transmission is completed, a start
bit is generated following to stop bit(s), and the next data is transmitted.
_______
• Set CTSi pin's port direction register to “0”.
Operation
Note