Queued Serial Multi-Channel Module
MPC561/MPC563 Reference Manual, Rev. 1.2
Freescale Semiconductor
15-53
where SCxBR is in the range {1, 2, 3, ..., 8191}.
The SCI receiver operates asynchronously. An internal clock is necessary to synchronize with an incoming
data stream. The SCI baud rate generator produces a receive time sampling clock with a frequency 16
times that of the SCI baud rate. The SCI determines the position of bit boundaries from transitions within
the received waveform, and adjusts sampling points to the proper positions within the bit period.
shows possible baud rates for a 40-MHz IMB3 clock. The maximum baud rate with this IMB3
clock speed is 1250 Kbaud.
15.7.7.4
Parity Checking
The PT bit in SCCxR1 selects either even (PT = 0) or odd (PT = 1) parity. PT affects received and
transmitted data. The PE bit in SCCxR1 determines whether parity checking is enabled (PE = 1) or
disabled (PE = 0). When PE is set, the MSB of data in a frame (i.e., the bit preceding the stop bit) is used
for the parity function. For transmitted data, a parity bit is generated. For received data, the parity bit is
checked. When parity checking is enabled, the PF bit in the SCI status register (SCxSR) is set if a parity
error is detected.
Enabling parity affects the number of data bits in a frame, which can in turn affect frame size.
shows possible data and parity formats.
Table 15-30. Examples of SCIx Baud Rates
1
1
These rates are based on a 40-MHz IMB3 clock.
Nominal
Baud Rate
Actual
Baud Rate
Percent
Error
Value of
SCxBR
1,250,000.00
57,600.00
38,400.00
32,768.00
28,800.00
19,200.00
14,400.00
9,600.00
4,800.00
2,400.00
1,200.00
600.00
300.00
1,250,000.00
56,818.18
37,878.79
32,894.74
29,069.77
19,230.77
14,367.81
9,615.38
4,807.69
2,399.23
1,199.62
600.09
299.98
0.00
-1.36
-1.36
0.39
0.94
0.16
-0.22
0.16
0.16
-0.03
-0.03
0.02
-0.01
1
22
33
38
43
65
87
130
260
521
1042
2083
4167
Table 15-31. Effect of Parity Checking on Data Size
M
PE
Result
0
0
8 data bits
0
1
7 data bits, 1 parity bit
SCxBR
f
SYS
32
x
SCI Baud Rate Desired
------------------------------------------------------------------------
=
Summary of Contents for MPC561
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Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
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