MC908AP32CFBE Datasheet, PDF (178/324 Pages) Freescale Semiconductor, Inc – The following revision history table summarizes changes contained in this document. For your convenience, the page number designators have been linked to the appropriate location.

Serial Communications Interface Module (SCI)
11.8.7 SCI Baud Rate Register
The baud rate register (SCBR) selects the baud rate for both the receiver and the transmitter.
Address:
Read:
Write:
Reset:
$0019
6
5
4
3
2
1
0
0
SCP1
SCP0
R
SCR2
SCR1
0
0
0
0
0
0
0
= Unimplemented
R
= Reserved
Figure 11-16. 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 11-6. Reset clears SCP1
and SCP0.
Table 11-6. 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 11-7. Reset clears
SCR2–SCR0.
Table 11-7. 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:
baud rate = ^{S-----C6---4-I---c-}_×--l--o-P--c--D-k-----s_×---o--B-u---Dr--c---e--
where:
SCI clock source = f_BUS or CGMXCLK
(selected by SCIBDSRC bit in CONFIG2 register)
PD = prescaler divisor
BD = baud rate divisor
MC68HC908AP Family Data Sheet, Rev. 4
178
Freescale Semiconductor