MC908JL8CDWE Datasheet, PDF (124/212 Pages) Freescale Semiconductor, Inc – Microcontrollers

Serial Communications Interface (SCI)
9.4.2 Transmitter
Figure 9-4 shows the structure of the SCI transmitter.
The baud rate clock source for the SCI is the bus clock.
INTERNAL BUS
BUS CLOCK
÷4
PRE- BAUD
SCALER DIVIDER
÷ 16
SCI DATA REGISTER
SCP1
SCP0
SCR1
SCR2
SCR0
11-BIT
TRANSMIT
SHIFT REGISTER
H876543210L
TxD
TXINV
M
PEN
PARITY
PTY
GENERATION
T8
DMATE
DMATE
SCTIE
SCTE
DMATE
SCTE
SCTIE
TC
TCIE
TRANSMITTER
CONTROL LOGIC
SCTE
SCTIE
TC
TCIE
SBK
LOOPS
ENSCI
TE
Figure 9-4. SCI Transmitter
9.4.2.1 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).
9.4.2.2 Character Transmission
During an SCI transmission, the transmit shift register shifts a character out to the TxD pin. The SCI data
register (SCDR) is the write-only buffer between the internal data bus and the transmit shift register. To
initiate an SCI transmission:
MC68HC908JL8/JK8 • MC68HC08JL8/JK8 • MC68HC908KL8 Data Sheet, Rev. 3.1
124
Freescale Semiconductor