M68HC16 Z SERIES
REGISTER SUMMARY
USER’S MANUAL
D-41
Writing a value of zero to SCBR disables the baud rate generator. There are 8191 dif-
ferent bauds available. The baud value depends on the value for SCBR and the sys-
tem clock, as used in the equation above.
shows possible baud rates for
a 16.78 MHz system clock. The maximum baud rate with this system clock speed is
524 kbaud.
More accurate baud rates can be obtained by varying the system clock frequency with
the VCO synthesizer. Each VCO speed increment adjusts the baud rate up or down
by 1/64 or 1.56%.
D.6.5 SCI Control Register 1
SCCR1 contains SCI configuration parameters, including transmitter and receiver en-
able bits, interrupt enable bits, and operating mode enable bits. SCCR0 can be read
or written at any time. The SCI can modify the RWU bit under certain circumstances.
Changing the value of SCCR1 bits during a transfer operation disrupts operation.
Bit 15 — Not Implemented
LOOPS — Loop Mode
0 = Normal SCI operation, no looping, feedback path disabled.
1 = Test SCI operation, looping, feedback path enabled.
WOMS — Wired-OR Mode for SCI Pins
0 = If configured as an output, TXD is a normal CMOS output.
1 = If configured as an output, TXD is an open-drain output.
Table D-32 Examples of SCI Baud Rates
Nominal
Baud Rate
Actual
Baud Rate
Percent Error
Value of SCBR
500,00.00
524,288.00
4.86
1
38,400.00
37,449.14
–2.48
14
32,768.00
32,768.00
0.00
16
19,200.00
19,418.07
1.14
27
9,600.00
9,532.51
–0.70
55
4,800.00
4,809.98
0.21
109
2,400.00
2,404.99
0.21
218
1,200.00
1,199.74
–0.02
437
600.00
599.87
–0.02
874
300.00
299.94
–0.02
1,748
110.00
110.01
0.01
4,766
64.00
64.00
0.01
8,191
SCCR1 — SCI Control Register 1
$YFFC0A
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
NOT USED
LOOPS
WOMS
ILT
PT
PE
M
WAKE
TIE
TCIE
RIE
ILIE
TE
RE
RWU
SBK
RESET:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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