MC68HC05B4 Datasheet, PDF (90/298 Pages) Motorola, Inc – High-density Complementary Metal Oxide Semiconductor (HCMOS) Microcomputer Unit

6.11.5 Baud rate register (BAUD)
The baud rate register provides the means to select two different or equivalent baud rates for the
transmitter and receiver.
SCI baud rate (BAUD)
Address bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
State
on reset
$000D SCP1 SCP0 SCT2 SCT1 SCT0 SCR2 SCR1 SCR0 00uu uuuu
SCP1, SCP0 — Serial prescaler select bits
These read/write bits determine the prescale factor, NP, by which the internal processor clock is
divided before it is applied to the transmitter and receiver rate control dividers, NT and NR. This
common prescaled output is used as the input to a divider that is controlled by the SCR0–SCR2
bits for the SCI receiver, and by the SCT0–SCT2 bits for the transmitter.
6
Table 6-3 First prescaler stage
SCP1
0
0
1
1
SCP0
0
1
0
1
Prescaler
division ratio (NP)
1
3
4
13
SCT2, SCT1,SCT0 — SCI rate select bits (transmitter)
These three read/write bits select the baud rates for the transmitter. The prescaler output is divided
by the factors shown in Table 6-4.
Table 6-4 Second prescaler stage (transmitter)
SCT2
0
0
0
0
1
1
1
1
SCT1
0
0
1
1
0
0
1
1
SCT0
0
1
0
1
0
1
0
1
Transmitter
division ratio (NT)
1
2
4
8
16
32
64
128
MOTOROLA
6-18
SERIAL COMMUNICATIONS INTERFACE
TPG
MC68HC05B6
Rev. 4