MC68HC05C8A Datasheet, PDF (71/158 Pages) Motorola, Inc – Microcontrollers

Serial Communications Interface (SCI)
SCI Data Format
9.4 SCI Data Format
The SCI uses the standard non-return-to-zero mark/space data format
illustrated in Figure 9-1.
8-BIT DATA FORMAT
(BIT M IN SCCR1 CLEAR)
NEXT
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
STOP
BIT
START
BIT
9-BIT DATA FORMAT
(BIT M IN SCCR1 SET)
NEXT
START
BIT ^{BIT 0}
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
STOP ^START
BIT
BIT
Figure 9-1. SCI Data Format
9.5 SCI Operation
The SCI allows full-duplex, asynchronous, RS232 or RS422 serial
communication between the MCU and remote devices, including other
MCUs. The SCI’s transmitter and receiver operate independently,
although they use the same baud-rate generator. This subsection
describes the operation of the SCI transmitter and receiver.
9.5.1 Transmitter
Figure 9-2 shows the structure of the SCI transmitter.
9.5.1.1 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).
MC68HC05C8A • MC68HCL05C8A • MC68HSC05C8A — Rev. 5.0
MOTOROLA
Serial Communications Interface (SCI)
Technical Data
71