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Serial Communications Interface (SCI)
Table 18-1. Pin Name Conventions
Generic Pin Names
Full Pin Names
RxD
PTE1/SCRxD
TxD
PTE0/SCTxD
18.4 Functional Description
Figure 18-1 shows the structure of the SCI module. The SCI allows full-duplex, asynchronous, NRZ serial
communication between 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
RxD
RECEIVE
SHIFT REGISTER
TRANSMIT
SHIFT REGISTER
TxD
SCTIE
TCIE
SCRIE
ILIE
TE
RE
RWU
SBK
CGMXCLK
TXINV
R8
T8
SCTE
TC
SCRF
IDLE
OR
NF
FE
PE
LOOPS
LOOPS
ENSCI
ORIE
NEIE
FEIE
PEIE
WAKEUP
CONTROL
RECEIVE
CONTROL
FLAG
CONTROL
TRANSMIT
CONTROL
BKF
ENSCI
RPF
÷4
PRE- BAUD RATE
SCALER GENERATOR
M
WAKE
ILTY
PEN
PTY
÷ 16
DATA SELECTION
CONTROL
Figure 18-1. SCI Module Block Diagram
MC68HC908AZ60A • MC68HC908AS60A • MC68HC908AS60E Data Sheet, Rev. 6
178
Freescale Semiconductor