mc68hc908as60 Freescale Semiconductor, Inc, mc68hc908as60 Datasheet - Page 228

• Manufacturer Part Number: mc68hc908as60
• Description: Mc68hc908as60 Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Serial Communications Interface (SCI)
17.5.1 Data Format
17.5.2 Transmitter
17.5.2.1 Character Length
17.5.2.2 Character Transmission
Technical Data
The SCI uses the standard non-return-to-zero mark/space data format
illustrated in
Figure 17-4
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).
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)
2. Enable the transmitter by writing a logic 1 to the transmitter enable
3. Clear the SCI transmitter empty bit (SCTE) by first reading SCI
4. Repeat step 3 for each subsequent transmission.
Freescale Semiconductor, Inc.
START
START
BIT
BIT
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in SCI control register 1 (SCC1).
bit (TE) in SCI control register 2 (SCC2).
status register 1 (SCS1) and then writing to the SCDR.
Serial Communications Interface (SCI)
BIT 0
BIT 0
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Figure
shows the structure of the SCI transmitter.
BIT 1
BIT 1
BIT 2
BIT 2
Figure 17-3. SCI Data Formats
17-3.
BIT 3
BIT 3
(BIT M IN SCC1 CLEAR)
8-BIT DATA FORMAT
9-BIT DATA FORMAT
(BIT M IN SCC1 SET)
BIT 4
BIT 4
BIT 5
BIT 5
BIT 6
BIT 6
OR DATA
PARITY
BIT 7
BIT 7
MC68HC908AS60 — Rev. 1.0
BIT
OR DATA
PARITY
STOP
BIT 8
BIT
BIT
START
STOP
NEXT
BIT
BIT
START
NEXT
BIT