Rev. 1.00, 09/03, page 442 of 704
16.4
Operation in Asynchronous Mode
Figure 16.2 shows the general format for asynchronous serial communication. One frame consists
of a start bit (low level), followed by transmit/receive data, a parity bit, and finally stop bits (high
level). In asynchronous serial communication, the transmission line is usually held in the mark
state (high level). The SCI monitors the transmission line, and when it detects the space state (low
level), recognizes a start bit and starts serial communication. Inside the SCI, the transmitter and
receiver are independent units, enabling full-duplex communication. Both the transmitter and the
receiver also have a double-buffered structure, so that data can be read from or written to during
transmission or reception, enabling continuous data transmission and reception.
LSB
Start
bit
MSB
Idle state
(mark state)
Stop bit
0
Transmit/receive data
D0
D1
D2
D3
D4
D5
D6
D7
0/1
1
1
1
1
Serial
data
Parity
bit
1 bit
1 or 2 bits
7 or 8 bits
1 bit or
none
One unit of transfer data (character or frame)
Figure 16.2 Data Format in Asynchronous Communication
(Example with 8-Bit Data, Parity, Two Stop Bits)
Summary of Contents for H8S/2437
Page 2: ...Rev 1 00 09 03 page ii of xxxviii ...
Page 8: ...Rev 1 00 09 03 page viii of xxxviii ...
Page 32: ...Rev 1 00 09 03 page xxxii of xxxviii ...
Page 38: ...Rev 1 00 09 03 page xxxviii of xxxviii ...
Page 168: ...Rev 1 00 09 03 page 130 of 704 ...
Page 336: ...Rev 1 00 09 03 page 298 of 704 ...
Page 402: ...Rev 1 00 09 03 page 364 of 704 ...
Page 454: ...Rev 1 00 09 03 page 416 of 704 ...
Page 512: ...Rev 1 00 09 03 page 474 of 704 ...
Page 562: ...Rev 1 00 09 03 page 524 of 704 ...
Page 648: ...Rev 1 00 09 03 page 610 of 704 ...
Page 672: ...Rev 1 00 09 03 page 634 of 704 ...
Page 732: ...Rev 1 00 09 03 page 694 of 704 ...
Page 742: ...Rev 1 00 09 03 page 704 of 704 ...
Page 745: ......
Page 746: ...H8S 2437 Group Hardware Manual REJ09B0059 0100Z ...