Serial Communications Interface Module (SCI)

Functional Description
MC68HC908MR16/MC68HC908MR32 — Rev. 4.0 Advance Information

MOTOROLA Serial Communications Interface Module (SCI) 279

14.4 Functional Description

Figure 14-1 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 transmitt er and receiver

of the SCI operate independently, althoug h they use the same baud rate

generator. During normal operation, the C PU mo nito rs the sta tus of the

SCI, writes the data to be transmitted, and processes received data.

Figure 14-1. SCI Module Block Diagram

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
PTF4/RxD PTF5/TxD
INTERNAL BUS
TXINV
LOOPS
÷ 4
÷ 16
PRE-
SCALER BAUD RATE
GENERATOR
fOP