MC68HC11F1 Datasheet, PDF (42/68 Pages) Motorola, Inc – Technical Summary 8-Bit Microcontroller

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
TRANSMITTER
BAUD RATE
CLOCK
SCDR Tx BUFFER
(WRITE ONLY)
10 (11) - BIT Tx SHIFT REGISTER
H (8) 7 6 5 4 3 2 1 0 L
DDD1
PIN BUFFER
PD1
AND CONTROL
TxD
TRANSMITTER
CONTROL LOGIC
FORCE PIN
DIRECTION (OUT)
SCCR1 SCI CONTROL 1
SCSR1 SCI STATUS 1
TDRE
TIE
TC
TCIE
SCCR2 SCI CONTROL 2
SCI Rx
QUESTS
SCI INTERRUPT
REQUEST
Figure 9 SCI Transmitter Block Diagram
INTERNAL
DATA BUS
MOTOROLA
42
MC68HC11F1/FC0
MC68HC11FTS/D