Serial Communications Interface Module (SCI)
Functional Description
13.3 Functional Description
Figure 13-2 shows the structure of the SCI module. The SCI allows full-duplex,
asynchronous, NRZ serial communication among the MCU and remote devices,
including other MCUs. The transmitter and receiver of the SCI operate
independently, although they use the same baud rate generator. During normal
operation, the CPU monitors the status of the SCI, writes the data to be
transmitted, and processes received data.
INTERNAL BUS
SCI DATA
REGISTER
SCI DATA
REGISTER
RECEIVE
SHIFT REGISTER
TRANSMIT
SHIFT REGISTER
PTF4/RxD
PTF5/TxD
TXINV
SCTIE
R8
T8
TCIE
SCRIE
ILIE
TE
SCTE
TC
RE
RWU
SBK
SCRF
IDLE
OR
NF
FE
PE
ORIE
NEIE
FEIE
PEIE
LOOPS
ENSCI
LOOPS
RECEIVE
CONTROL
FLAG
CONTROL
TRANSMIT
CONTROL
WAKEUP
CONTROL
M
BKF
RPF
ENSCI
WAKE
ILTY
PEN
PTY
PRE- BAUD RATE
SCALER GENERATOR
fOP
÷ 4
DATA SELECTION
CONTROL
÷ 16
Figure 13-2. SCI Module Block Diagram
MC68HC908MR32 • MC68HC908MR16 — Rev. 6.0
MOTOROLA Serial Communications Interface Module (SCI)
Data Sheet
171
FREESCALE [ Freescale ]
