SERIAL COMMUNICATION INTERFACE (SCI)
MOTOROLA
PORT C
6 - 33
the SCI. The asynchronous SCI baud rates show a baud rate error for the fixed os-
cillator frequency (see Table 6-3 (a)). These small-percentage baud rate errors
should allow most UARTs to synchronize. The synchronous applications usually re-
quire exact frequencies, which require that the crystal frequency be chosen carefully
(see Table 6-4 (a) and Table 6-4 (b)).
An alternative to selecting the system clock to accommodate the SCI requirements is to
provide an external clock to the SCI. For example, a 2.048 MHz bit rate requires a CPU
clock of 32.768 MHz. An application may need a 40 MHz CPU clock and an external clock
for the SCI.
1. PERFORM HARDWARE OR SOFTWARE RESET.
2. PROGRAM SCI CONTROL REGISTERS:
a)
SCI INTERFACE CONTROL REGISTER — X:$FFF0
b)
SCI CLOCK CONTROL REGISTER — X:$FFF2
3. CONFIGURE AT LEAST ONE PORT C CONTROL BIT AS SCI.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
CC
0
23
0
X:$FFE1
PORT C CONTROL
REGISTER (PCC)
CCx
Function
0
GPIO
1
Serial Interface
CC
1
CC
2
CC
3
CC
4
CC
5
CC
6
CC
7
CC
8
SCLK
TXD
RXD
SCI
4. SCI IS NOW ACTIVE.
Figure 6-14 SCI Initialization Procedure
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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