Freescale Semiconductor, Inc.
OR — Overrun Error Flag
OR is set if a new character is received before a previously received character is read
from SCDR. Clear the OR flag by reading SCSR and then reading SCDR.
0 = No overrun
1 = Overrun detected
NF — Noise Error Flag
NF is set if majority sample logic detects anything other than a unanimous decision.
Clear NF by reading SCSR and then reading SCDR.
0 = Unanimous decision
1 = Noise detected
FE — Framing Error
FE is set when a zero is detected where a stop bit was expected. Clear the FE flag by
reading SCSR and then reading SCDR.
0 = Stop bit detected
1 = Zero detected
Bit 0 — Not implemented
Always reads zero
7.6.5 Baud Rate Register
Use this register to select different baud rates for the SCI system. The SCP[1:0] bits
select the prescaler rate for the SCR[2:0] bits. Together, these five bits provide multi-
ple baud rate combinations for a given crystal frequency. Normally, this register is writ-
ten 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 Table 7-1 and Table 7-2 for normal
baud rate selections.
BAUD — Baud Rate
$102B
Bit 7
6
—
0
5
SCP1
0
4
SCP0
0
3
RCKB
0
2
SCR2
U
1
SCR1
U
Bit 0
SCR0
U
TCLR
RESET:
0
TCLR — Clear Baud Rate Counters (Test)
SCP[1:0] — SCI Baud Rate Prescaler Selects
Refer to the SCI baud rate generator block diagram.
Table 7-1 Baud Rate Prescaler Selection
Prescaler
Divide Internal
Crystal Frequency (MHz)
SCP1
SCP0
Clock By
4.0
4.9152
76800
25600
19200
5907
8.0
12.0
187500
62500
46875
14423
16.0
20.0
0
0
1
1
0
1
0
1
1
3
62500
20833
15625
4800
125000
41667
31250
9600
25000
83332
62500
19200
312500
104165
78125
24000
4
13
SERIAL COMMUNICATIONS INTERFACE
MC68HC11F1
7-8
TECHNICAL DATA
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