MC68HC908KX8 Datasheet, PDF (184/310 Pages) Motorola, Inc – Microcontrollers

Serial Communications Interface Module (SCI)
14.5.1 Data Format
The SCI uses the standard non-return-to-zero mark/space data format
illustrated in Figure 14-3.
START
BIT
BIT 0
BIT 1
BIT 2
8-BIT DATA FORMAT
BIT M IN SCC1 CLEAR
PARITY
OR DATA
BIT
BIT 3 BIT 4 BIT 5 BIT 6 BIT 7 STOP
BIT
NEXT
START
BIT
START
BIT BIT 0
BIT 1
BIT 2
9-BIT DATA FORMAT
BIT M IN SCC1 SET
BIT 3 BIT 4 BIT 5 BIT 6
PARITY
OR DATA
BIT
BIT 7 BIT 8 STOP
BIT
NEXT
START
BIT
Figure 14-3. SCI Data Formats
14.5.2 Transmitter
Figure 14-4 shows the structure of the SCI transmitter.
14.5.2.1 Character Length
The transmitter can accommodate either 8-bit or 9-bit data. The state of
the M bit in SCI control register 1 (SCC1) determines character length.
When transmitting 9-bit data, bit T8 in SCI control register 3 (SCC3) is
the ninth bit (bit 8).
14.5.2.2 Character Transmission
During an SCI transmission, the transmit shift register shifts a character
out to the TxD pin. The SCI data register (SCDR) is the write-only buffer
between the internal data bus and the transmit shift register. To initiate
an SCI transmission:
1. Enable the SCI by writing a logic 1 to the enable SCI bit (ENSCI)
in SCI control register 1 (SCC1).
2. Enable the transmitter by writing a logic 1 to the transmitter enable
bit (TE) in SCI control register 2 (SCC2).
Technical Data
184
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 — Rev. 1.0
Serial Communications Interface Module (SCI)
MOTOROLA