
Serial Communications Interface Module (SCI)
MC68HC908AP A-Family Data Sheet, Rev. 3
154
Freescale Semiconductor
11.4.1 Data Format
The SCI uses the standard non-return-to-zero mark/space data format illustrated in
Figure 11-3.
Figure 11-3. SCI Data Formats
11.4.2 Transmitter
Figure 11-4 shows the structure of the SCI transmitter.
The baud rate clock source for the SCI can be selected via the configuration bit, SCIBDSRC. Source
Figure 11-4. SCI Transmitter
BIT 5
START
BIT
BIT 0
BIT 1
NEXT
STOP
BIT
START
BIT
8-BIT DATA FORMAT
BIT M IN SCC1 CLEAR
START
BIT
BIT 0
NEXT
STOP
BIT
START
BIT
9-BIT DATA FORMAT
BIT M IN SCC1 SET
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
BIT 2
BIT 3
BIT 4
BIT 6
BIT 7
PARITY
BIT
PARITY
BIT
DMATE
SCTE
PEN
PTY
H
876543210L
11-BIT
TRANSMIT
STOP
START
T8
DMATE
SCTE
SCTIE
TCIE
SBK
TC
PARITY
GENERATION
MSB
SCI DATA REGISTER
LOAD
FROM
SCDR
SHIFT
ENABLE
PREAMBLE
ALL
1s
BREAK
ALL
0s
TRANSMITTER
CONTROL LOGIC
SHIFT REGISTER
DMATE
TC
SCTIE
TCIE
SCTE
TRANSMITTER
CPU
INTERRUPT
REQUEST
TRANSMITTER
DMA
SERVICE
REQUEST
M
ENSCI
LOOPS
TE
TXINV
INTERNAL BUS
÷ 4
PRE-
SCALER
SCP1
SCP0
SCR2
SCR1
SCR0
BAUD
DIVIDER
÷ 16
SCTIE
CGMXCLK
IT12
A
B
SL
X
SL = 0 => X = A
SL = 1 => X = B
SCIBDSRC
FROM
CONFIG2
TxD