Datasheet

Serial Communications Interface (SCI)
MC68HC908AZ60A • MC68HC908AS60A • MC68HC908AS60E Data Sheet, Rev. 6
178 Freescale Semiconductor
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.
Figure 18-1. SCI Module Block Diagram
Table 18-1. Pin Name Conventions
Generic Pin Names RxD TxD
Full Pin Names PTE1/SCRxD PTE0/SCTxD
SCTE
TC
SCRF
IDLE
OR
NF
FE
PE
SCTIE
TCIE
SCRIE
ILIE
TE
RE
RWU
SBK
R8
T8
ORIE
FEIE
PEIE
BKF
RPF
SCI DATA
RECEIVE
SHIFT REGISTER
SCI DATA
REGISTER
TRANSMIT
SHIFT REGISTER
NEIE
M
WAKE
ILTY
FLAG
CONTROL
TRANSMIT
CONTROL
RECEIVE
CONTROL
DATA SELECTION
CONTROL
WAKEUP
PTY
PEN
REGISTER
TRANSMITTER
INTERRUPT
CONTROL
RECEIVER
INTERRUPT
CONTROL
ERROR
INTERRUPT
CONTROL
CONTROL
ENSCI
LOOPS
ENSCI
INTERNAL BUS
TXINV
LOOPS
÷ 4
÷ 16
PRE-
SCALER
BAUD RATE
GENERATOR
CGMXCLK
RxD
TxD