Datasheet

Serial Communications Interface Module (SCI)
MC68HC908AP Family Data Sheet, Rev. 4
158 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
selection values are shown in Figure 11-4.
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
H876543210L
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
A
B
SL
X
SL = 0 => X = A
SL = 1 => X = B
SCIBDSRC
FROM
CONFIG2
TxD
BUS CLOCK