MC68HC705 MOTOROLA [Motorola, Inc], MC68HC705 Datasheet - Page 121

• Manufacturer Part Number: MC68HC705
• Description: HCMOS Microcontroller Unit
• Manufacturer: MOTOROLA [Motorola, Inc]

10.5 SCI Operation
10.5.1 Transmitter
MC68HC705C8A — Rev. 2.0
MOTOROLA
START
START
BIT
BIT
BIT 0
BIT 0
The SCI allows full-duplex, asynchronous, RS232 or RS422 serial
communication between the MCU and remote devices, including other
MCUs. The transmitter and receiver of the SCI operate independently,
although they use the same baud-rate generator. This subsection
describes the operation of the SCI transmitter and receiver.
Figure 10-2
summary of the SCI transmitter input/output (I/O) registers.
BIT 1
BIT 1
•
•
Character Length — The transmitter can accommodate either
8-bit or 9-bit data. The state of the M bit in SCI control register 1
(SCCR1) determines character length. When transmitting 9-bit
data, bit T8 in SCCR1 is the ninth bit (bit 8).
Character Transmission — During transmission, the transmit shift
register shifts a character out to the PD1/TDO pin. The SCI data
register (SCDR) is the write-only buffer between the internal data
bus and the transmit shift register.
BIT 2
BIT 2
Serial Communications Interface (SCI)
Figure 10-1. SCI Data Format
shows the structure of the SCI transmitter.
BIT 3
BIT 3
(BIT M IN SCCR1 CLEAR)
(BIT M IN SCCR1 SET)
8-BIT DATA FORMAT
9-BIT DATA FORMAT
BIT 4
BIT 4
BIT 5
BIT 5
BIT 6
BIT 6
BIT 7
BIT 7
Serial Communications Interface (SCI)
STOP
BIT 8
BIT
START
NEXT
STOP
BIT
BIT
Figure 10-3
START
NEXT
BIT
Technical Data
SCI Operation
is a
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