HD64336901G Renesas Technology, HD64336901G Datasheet - Page 230

• Manufacturer Part Number: HD64336901G
• Description: (HD64xxx Series) 16-BIT MICROCONTROLLER
• Manufacturer: Renesas Technology

14.4
Figure 14.3 shows the general format for asynchronous serial communication. One character (or
frame) consists of a start bit (low level), followed by data (in LSB-first order), a parity bit (high or
low level), and finally stop bits (high level). Inside the SCI3, the transmitter and receiver are
independent units, enabling full-duplex. Both the transmitter and the receiver also have a double-
buffered structure, so data can be read or written during transmission or reception, enabling
continuous data transfer.
14.4.1
Either an internal clock generated by the on-chip baud rate generator or an external clock input at
the SCK3 pin can be selected as the SCI3’s serial clock, according to the setting of the COM bit in
SMR and the CKE0 and CKE1 bits in SCR3. When an external clock is input at the SCK3 pin, the
clock frequency should be 16 times the bit rate used.
When SCI3 is operated on an internal clock, the clock can be output from the SCK3 pin. The
frequency of the clock output in this case is equal to the bit rate, and the phase is such that the
rising edge of the clock is in the middle of the transmit data, as shown in figure 14.4.
Rev. 1.00, 11/03, page 202 of 376
Clock
Serial data
Serial
data
Figure 14.4 Relationship between Output Clock and Transfer Data Phase
Operation in Asynchronous Mode
Clock
(Asynchronous Mode)(Example with 8-Bit Data, Parity, Two Stop Bits)
Start
bit
1 bit
Figure 14.3 Data Format in Asynchronous Communication
LSB
0
D0
One unit of transfer data (character or frame)
D1
Transmit/receive data
D2
7 or 8 bits
D3
1 character (frame)
D4
D5
D6
MSB
D7
Parity
bit
1 bit,
or none
0/1
1
Stop bit
1 or
2 bits
1
Mark state
1