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Section 10 Serial Communication Interface
Rev. 6.00 Sep 12, 2006 page 313 of 526
REJ09B0326-0600
10.3.4
Operation in Asynchronous Mode
In asynchronous mode, serial communication is performed with synchronization provided
character by character. A start bit indicating the start of communication and one or two stop bits
indicating the end of communication are added to each character before it is sent.
SCI3 has separate transmission and reception units, allowing full-duplex communication. As the
transmission and reception units are both double-buffered, data can be written during transmission
and read during reception, making possible continuous transmission and reception.
Data Transfer Format:
The general data transfer format in asynchronous communication is
shown in figure 10.8.
Serial
data
Start
bit
1 bit
Transmit/receive data
Parity
bit
Stop
bit(s)
7 or 8 bits
One transfer data unit (character or frame)
1 bit
or none
1 or 2 bits
Mark
state
1
(MSB)
(LSB)
Figure 10.8 Data Format in Asynchronous Communication
In asynchronous communication, the communication line is normally in the mark state (high
level). SCI3 monitors the communication line and when it detects a space (low level), identifies
this as a start bit and begins serial data communication.
One transfer data character consists of a start bit (low level), followed by transmit/receive data
(LSB-first format, starting from the least significant bit), a parity bit (high or low level), and
finally one or two stop bits (high level).
In asynchronous mode, synchronization is performed by the falling edge of the start bit during
reception. The data is sampled on the 8th pulse of a clock with a frequency 16 times the bit period,
so that the transfer data is latched at the center of each bit.
Summary of Contents for F-ZTAT H8/3642A Series
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Page 124: ...Section 5 Power Down Modes Rev 6 00 Sep 12 2006 page 102 of 526 REJ09B0326 0600 ...
Page 188: ...Section 6 ROM Rev 6 00 Sep 12 2006 page 166 of 526 REJ09B0326 0600 ...
Page 190: ...Section 7 RAM Rev 6 00 Sep 12 2006 page 168 of 526 REJ09B0326 0600 ...
Page 298: ...Section 9 Timers Rev 6 00 Sep 12 2006 page 276 of 526 REJ09B0326 0600 ...
Page 378: ...Section 12 A D Converter Rev 6 00 Sep 12 2006 page 356 of 526 REJ09B0326 0600 ...
Page 446: ...Section 13 Electrical Characteristics Rev 6 00 Sep 12 2006 page 424 of 526 REJ09B0326 0600 ...