MC68HC908GP32_08 Datasheet, PDF (154/266 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Serial Communications Interface Module (SCI)
Address:
Read:
Write:
Reset:
$0019
Bit 7
6
5
4
3
2
1
SCP1
SCP0
R
SCR2
SCR1
0
0
0
0
0
0
0
= Unimplemented
R = Reserved
Figure 13-16. SCI Baud Rate Register (SCBR)
Bit 0
SCR0
0
SCP1 and SCP0 — SCI Baud Rate Prescaler Bits
These read/write bits select the baud rate prescaler divisor as shown in Table 13-6. Reset clears SCP1
and SCP0.
Table 13-6. SCI Baud Rate Prescaling
SCP1 and SCP0
00
01
10
11
Prescaler Divisor (PD)
1
3
4
13
SCR2–SCR0 — SCI Baud Rate Select Bits
These read/write bits select the SCI baud rate divisor as shown in Table 13-7. Reset clears
SCR2–SCR0.
Table 13-7. SCI Baud Rate Selection
SCR2, SCR1, and SCR0
000
001
010
011
100
101
110
111
Baud Rate Divisor (BD)
1
2
4
8
16
32
64
128
Use this formula to calculate the SCI baud rate:
SCI clock source
baud rate = --------------------------------------------
64 × PD × BD
where:
SCI clock source = f_BUS or CGMXCLK (selected by SCIBDSRC bit in CONFIG2 register)
PD = prescaler divisor
BD = baud rate divisor
Table 13-8 shows the SCI baud rates that can be generated with a 4.9152-MHz bus clock when f_BUS is
selected as SCI clock source.
MC68HC908GP32 Data Sheet, Rev. 10
154
Freescale Semiconductor