MC68HC11F1 Datasheet, PDF (45/68 Pages) Motorola, Inc – Technical Summary 8-Bit Microcontroller

Figure 11 illustrates the SCI baud rate timing chain. The prescaler select bits determine the highest
baud rate. The rate select bits determine additional divide-by-two stages to arrive at the receiver timing
(RT) clock rate. The baud rate clock is the result of dividing the RT clock by 16.
EXTAL
XTAL
OSCILLATOR
AND
CLOCK GENERATOR
(÷ 4)
E
INTERNAL BUS CLOCK (PH2)
÷3
÷4
÷ 13
÷9
X00
001
X10
X11
101
SCR[2:0]
0:0:0
÷2
0:0:1
÷2
0:1:0
÷2
0:1:1
÷2
1:0:0
÷2
1:0:1
÷2
1:1:0
÷2
1:1:1
SCI Receive Baud Rate (16x)
÷ 16
SCI Transmit Baud Rate (1x)
Figure 11 SCI Baud Rate Generator Block Diagram
MC68HC11F1/FC0
MC68HC11FTS/D
MOTOROLA
45