MC68HC908GP32_08 Datasheet, PDF (135/266 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Functional Description
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.
SCIBDSRC
FROM
CONFIG2
CGMXCLK
BUS CLOCK
SL
X
SL = 0 => SCICLK = CGMXCLK
SL = 1 => SCICLK = BUS CLOCK
INTERNAL BUS
÷4
PRE- BAUD
SCALER DIVIDER
÷ 16
SCP1
SCP0
SCR2
SCR1
SCR0
TXINV
SCI DATA REGISTER
11-BIT
TRANSMIT
SHIFT REGISTER
H876543210L
PTE0/TxD
M
PEN
PARITY
PTY
GENERATION
T8
TRANSMITTER CPU
INTERRUPT REQUEST
TRANSMITTER
CONTROL LOGIC
SCTE
SCTIE
TC
TCIE
SCTE
SCTIE
TC
TCIE
SBK
LOOPS
ENSCI
TE
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).
MC68HC908GP32 Data Sheet, Rev. 10
Freescale Semiconductor
135