Datasheet

Serial Communications Interface Module (SCI)
MC68HC908AP Family Data Sheet, Rev. 4
178 Freescale Semiconductor
11.8.7 SCI Baud Rate Register
The baud rate register (SCBR) selects the baud rate for both the receiver and the transmitter.
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.
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.
Use this formula to calculate the SCI baud rate:
where:
SCI clock source = f
BUS
or CGMXCLK
(selected by SCIBDSRC bit in CONFIG2 register)
PD = prescaler divisor
BD = baud rate divisor
Address: $0019 654321Bit 0
Read: 0 0
SCP1 SCP0 R SCR2 SCR1 SCR0
Write:
Reset:00000000
= Unimplemented R = Reserved
Figure 11-16. SCI Baud Rate Register (SCBR)
Table 11-6. SCI Baud Rate Prescaling
SCP1 and SCP0 Prescaler Divisor (PD)
00 1
01 3
10 4
11 13
Table 11-7. SCI Baud Rate Selection
SCR2, SCR1, and SCR0 Baud Rate Divisor (BD)
000 1
001 2
010 4
011 8
100 16
101 32
110 64
111 128
baud rate
SCI clock source
64 PD BD××
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