MC68HCP11 Datasheet, PDF (23/45 Pages) Motorola, Inc – 8-Bit Microcontroller

6 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 MC68HC11A8. It has a standard NRZ format (one start,
eight or nine data, and one stop bit) and several baud rates available. The SCI transmitter and receiver
are independent, but use the same data format and bit rate.
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
8
SCCR1 SCI CONTROL 1
TRANSMITTER
CONTROL LOGIC
FORCE PIN
DIRECTION (OUT)
8
SCSR INTERRUPT STATUS
8
TDRE
TIE
TC
TCIE
SCCR2 SCI CONTROL 2
SCI Rx
REQUESTS
SCI INTERRUPT
REQUEST
Figure 6 SCI Transmitter Block Diagram
INTERNAL
DATA BUS
11 SCI TX BLOCK
MC68HC11A8
MC68HC11A8TS/D
MOTOROLA
23