mc68hc11d0 Freescale Semiconductor, Inc, mc68hc11d0 Datasheet - Page 74

• Manufacturer Part Number: mc68hc11d0
• Description: Mc68hc11d0 Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

BAUD — Baud Rate
NF — Noise Error Flag
FE — Framing Error
7.6.5 Baud Rate Register (BAUD)
TCLR — Clear Baud Rate Counters (Test)
RCKB — SCI Baud Rate Clock Check (Test)
SCP1, SCP0 — SCI Baud Rate Prescaler Selects
SCR[2:0] — SCI Baud Rate Selects
7-8
RESET:
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.
Use this register to select different baud rates for the SCI system. The SCP[1:0] bits
function as a prescaler for the SCR[2:0] 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 Table 7-1 and Table 7-2 for normal baud
rate selections.
These two bits select a prescale factor for the SCI baud rate generator that determines
the highest possible baud rate.
These three bits select receiver and transmitter bit rate based on output from baud rate
prescaler stage.
0 = Unanimous decision
1 = Noise detected
0 = Stop bit detected
1 = 0 detected
TCLR
Bit 7
0
SCP[1:0]
0 0
0 1
1 0
1 1
Freescale Semiconductor, Inc.
6
0
0
Table 7-1 Baud Rate Prescale Selects
For More Information On This Product,
SERIAL COMMUNICATIONS INTERFACE
Internal Clock
Divide
SCP1
By
13
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1
3
4
5
0
15.625 K
SCP0
4.0 MHz
62.50 K
20.83 K
(Baud)
4800
4
0
Crystal Frequency in MHz
8.0 MHz
125.0 K
41.67 K
31.25 K
(Baud)
RCKB
9600
3
0
10.0 MHz
156.25 K
52.08 K
12.02 K
(Baud)
38.4 K
SCR2
U
2
12.0 MHz
187.5 K
46.88 K
14.42 K
(Baud)
62.5 K
SCR1
TECHNICAL DATA
U
1
$002B
SCR0
Bit 0
U