m37905 Renesas Electronics Corporation., m37905 Datasheet - Page 300

• Manufacturer Part Number: m37905
• Description: Mitsubishi 16-bit Single-chip Microcomputer 7700 Family / 7900 Series
• Manufacturer: Renesas Electronics Corporation.

11.4.4 Transmit operation
When the receive conditions described in section “11.4.3 Method of transmission” have been satisfied,
a transfer clock is generated, and the following operations are automatically performed after 1 cycle of the
transfer clock or less has passed.
•The UARTi transmit buffer register’s contents are transferred to the UARTi transmit register.
•The transmit buffer empty flag is set to “1.”
•The transmit register empty flag is cleared to “0.”
•A UARTi transmit interrupt request occurs, and the interrupt request bit is set to “1.”
The transmit operations are described below:
When the transmit conditions for the next data are satisfied in step
the stop bit, and the next data is transmitted. When performing transmission continuously, be sure to set
the next transmit data in the UARTi transmit buffer register during transmission (i.e. when the transmit
register empty flag = “0”). When the transmit conditions for the next data are not satisfied, the TxD
outputs “H” level and the transfer clock stops.
Figures 11.4.7 and 11.4.8 show examples of transmit timing when the transfer data length = 8 bits, and
Figure 11.4.9 shows an example of transmit timing when the transfer data length = 9 bits.
The transmit register empty flag is set to “1” at the center of the stop bit (or the second stop bit if 2 stop
Data in the UARTi transmit register is transmitted from the TxD
This data is transmitted bit by bit sequentially in order of ST
bits selected). This indicates completion of transmission. Additionally, whether the transmit conditions
for the next data are satisfied or not is examined.
SP according to the transfer data format.
7905 Group User’s Manual Rev.1.0
11.4 Clock asynchronous serial I/O (UART) mode
DATA (LSB)
i
pin.
, the start bit is generated following
••• DATA (MSB)
SERIAL I/O
11-45
PAR
i
pin