Datasheet

Functional Description
MC68HC908GP32 Data Sheet, Rev. 10
Freescale Semiconductor 135
13.4.2 Transmitter
Figure 13-4 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 13-4.
Figure 13-4. SCI Transmitter Block Diagram
13.4.2.1 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).
PEN
PTY
H876543210L
11-BIT
TRANSMIT
STOP START
T8
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
TC
SCTIE
TCIE
SCTE
TRANSMITTER CPU
M
ENSCI
LOOPS
TE
PTE0/TxD
TXINV
INTERNAL BUS
÷ 4
PRE-
SCALER
SCP1
SCP0
SCR1
SCR2
SCR0
BAUD
DIVIDER
÷ 16
CGMXCLK
BUS CLOCK
SL
X
SL = 0 => SCICLK = CGMXCLK
SL = 1 => SCICLK = BUS CLOCK
SCIBDSRC
FROM
CONFIG2
INTERRUPT REQUEST