Serial Communications Interface Module (SCI)
11.4.1 Data Format
The SCI uses the standard non-return-to-zero mark/space data format illustrated in Figure 11-3.
8-BIT DATA FORMAT
BIT M IN SCC1 CLEAR
PARITY
BIT
NEXT
START
BIT
START
BIT
STOP
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
9-BIT DATA FORMAT
BIT M IN SCC1 SET
PARITY
BIT
NEXT
START
BIT
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 8
STOP
BIT
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
selection values are shown in Figure 11-4.
INTERNAL BUS
PRE- BAUD
SCALER DIVIDER
÷ 16
÷ 4
SCI DATA REGISTER
SCIBDSRC
FROM
CONFIG2
SCP1
SCP0
SCR1
SCR2
SCR0
11-BIT
TRANSMIT
SHIFT REGISTER
H
8
7
6
5
4
3
2
1
0
L
TxD
SL
A
CGMXCLK
BUS CLOCK
X
B
SL = 0 => X = A
SL = 1 => X = B
TXINV
M
PEN
PTY
PARITY
GENERATION
T8
DMATE
TRANSMITTER
CONTROL LOGIC
DMATE
SCTIE
SCTE
SCTE
SBK
DMATE
SCTE
LOOPS
ENSCI
TE
SCTIE
SCTIE
TC
TC
TCIE
TCIE
Figure 11-4. SCI Transmitter
MC68HC908AP Family Data Sheet, Rev. 4
158
Freescale Semiconductor
FREESCALE [ Freescale ]
