MOTOROLA
MC68HC11F1/FC0
42
MC68HC11FTS/D
9 Serial Communications Interface (SCI)
The SCI, a universal asynchronous receiver transmitter (UART) serial communications interface, is one
of two independent serial I/O subsystems in the MC68HC11F1 and MC68HC11FC0. The SCI has a
standard non-return to zero (NRZ) format (one start bit, eight or nine data bits, and one stop bit) and
several selectable baud rates. The transmitter and receiver are independent but use the same data for-
mat and bit rate.
9.1 SCI Block Diagrams
Figure 9 SCI Transmitter Block Diagram
TC
TDRE
SCSR1
SCI STATUS 1
SCCR2
SCI CONTROL 2
TRANSMITTER
CONTROL LOGIC
TCIE
TC
TIE
TDRE
SCI Rx
QUESTS
SCI INTERRUPT
REQUEST
INTERNAL
DATA BUS
PIN BUFFER
AND CONTROL
H
10 (11) - BIT Tx SHIFT REGISTER
DDD1
SCDR Tx BUFFER
TRANSFER Tx BUFFER
SHIFT ENABLE
JAM ENABLE
PREAMBLE—JAM 1s
BREAK—JAM 0s
(WRITE ONLY)
FORCE PIN
DIRECTION (OUT)
SIZE 8/9
M
SCCR1
SCI CONTROL 1
TRANSMITTER
BAUD RATE
CLOCK
TIE
TCIE
TE
SBK
(8) 7
6
5
4
3
2
1
0
L
PD1
TxD
T8
R8
WAKE
RDRF
IDLE
OR
NF
FE
RIE
ILIE
RE
RWU