HD6413008F RENESAS [Renesas Technology Corp], HD6413008F Datasheet - Page 397

• Manufacturer Part Number: HD6413008F
• Description: Renesas 16-Bit Single-Chip Microcomputer H8 Family/H8/300H Series
• Manufacturer: RENESAS [Renesas Technology Corp]

12.3.2
In asynchronous mode, each transmitted or received character begins with a start bit and ends with
one or two stop bits. Serial communication is synchronized one character at a time.
The transmitting and receiving sections of the SCI are independent, so full-duplex communication
is possible. The transmitter and the receiver are both double-buffered, so data can be written and
read while transmitting and receiving are in progress, enabling continuous transmitting and
receiving.
Figure 12.2 shows the general format of asynchronous serial communication. In asynchronous
serial communication the communication line is normally held in the mark (high) state. The SCI
monitors the line and starts serial communication when the line goes to the space (low) state,
indicating a start bit. One serial character consists of a start bit (low), data (LSB first), parity bit
(high or low), and one or two stop bits (high), in that order.
When receiving in asynchronous mode, the SCI synchronizes at the falling edge of the start bit.
The SCI samples each data bit on the eighth pulse of a clock with a frequency 16 times the bit rate.
Receive data is latched at the center of each bit.
Communication Formats: Table 12.10 shows the 12 communication formats that can be selected
in asynchronous mode. The format is selected by settings in SMR.
Serial
data
1
Operation in Asynchronous Mode
Start
bit
1 bit
0
(LSB)
Figure 12.2 Data Format in Asynchronous Communication
D0
(Example: 8-Bit Data with Parity and 2 Stop Bits)
D1
One unit of data (character or frame)
D2
Transmit or receive data
D3
7 or 8 bits
D4
D5
Rev.4.00 Aug. 20, 2007 Page 353 of 638
D6
12. Serial Communication Interface
(MSB)
D7
Parity
bit
1 bit,
none
0/1
or
Stop bit(s)
1 or 2 bits
REJ09B0395-0400
1
Idle (mark) state
1
1