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UART
Mitsubishi microcomputers
M16C / 62 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
358
In transmitting data in UART mode, choose functions from those listed in Table 2.5.4. Operations of the
circled items are described below. Figure 2.5.8 shows the operation timing, and Figures 2.5.9 and 2.5.10
show the set-up procedures.
2.5.2 Operation of Serial I/O (transmission in UART mode)
Item
Set-up
Transfer clock
source
(Note 2)
Internal clock (f1 / f8 / f32)
External clock (CLKi pin)
CTS function
CTS function enabled
CTS function disabled
O
Transmission
interrupt factor
Transmission buffer empty
Transmission complete
O
CTS / RTS
separation function
(Note 1)
Pin shared by CTS and RTS
CTS and RTS separate
O
Sleep mode
(Note 2)
Sleep mode off
Sleep mode selected
O
Item
Set-up
Data logic select
function
(Note 3)
No reverse
Reverse
O
TXD, RXD I/O
polarity reverse bit
(Note 3)
No reverse
Reverse
O
Bus collision
detection function
(Note 3)
O
Not selected
Selected
Table 2.5.4. Choosed functions
_______________
Note 1: UART0 only. (UART1 CTS/RTS function cannot be used when this function is selected.)
Note 2: UART0, UART1 only.
Note 3: UART2 only.
(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.
Operation