mc68hc11d0cfn2 Freescale Semiconductor, Inc, mc68hc11d0cfn2 Datasheet - Page 81

• Manufacturer Part Number: mc68hc11d0cfn2
• Description: M68hc11 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

6.7.5 Baud Rate Register
MC68HC711D3 — Rev. 2
MOTOROLA
NF — Noise Error Flag
FE — Framing Error Bit
The baud rate register (BAUD) is used to select different baud rates for the SCI
system. The SCP1 and SCP0 bits function as a prescaler for the SCR2–SCR0 bits.
Together, these five bits provide multiple baud rate combinations for a given crystal
frequency. Normally, this register is written once during initialization. The prescaler
is set to its fastest rate by default out of reset and can be changed at any time.
Refer to
TCLR — Clear Baud Rate Counters (Test)
RCKB — SCI Baud Rate Clock Check (Test)
SCP1 and SCP0 — SCI Baud Rate Prescaler Select Bits
NF is set if majority sample logic detects anything other than a unanimous
decision. Clear NF by reading SCSR with NF set and then reading SCDR.
FE is set when a 0 is detected where a stop bit was expected. Clear the FE flag
by reading SCSR with FE set and then reading SCDR.
These two bits select a prescale factor for the SCI baud rate generator that
determines the highest possible baud rate.
and SCP0
Address:
Reset:
SCP1
Read:
Write:
0 = Unanimous decision
1 = Noise detected
0 = Stop bit detected
1 = Zero detected
0 0
0 1
1 0
1 1
Freescale Semiconductor, Inc.
Table 6-1
For More Information On This Product,
U = Unaffected
$002B
TCLR
Bit 7
Serial Communications Interface (SCI)
0
Internal Clock
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and
Divide
Table 6-1. Baud Rate Prescale Selects
Figure 6-7. Baud Rate Register (BAUD)
By
13
1
3
4
6
0
0
Table 6-2
SCP1
5
0
for normal baud rate selections.
15.625 K
4.0 MHz
62.50 K
20.83 K
(Baud)
4800
SCP0
4
0
Crystal Frequency in MHz
8.0 MHz
Serial Communications Interface (SCI)
125.0 K
41.67 K
31.25 K
(Baud)
9600
RCKB
3
0
SCR2
10.0 MHz
156.25 K
52.08 K
12.02 K
(Baud)
38.4 K
U
2
SCR1
U
1
SCI Registers
12.0 MHz
187.5 K
46.88 K
14.42 K
(Baud)
62.5 K
Data Sheet
SCR0
Bit 0
U
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