mpc823rg Freescale Semiconductor, Inc, mpc823rg Datasheet - Page 611

• Manufacturer Part Number: mpc823rg
• Description: Mpc823 Powerquicc Integrated Communications Processor For Portable Systems
• Manufacturer: Freescale Semiconductor, Inc

16.8.3 UART Baud Rate Examples
For synchronous communication using the internal baud rate generator, the BRGOx output
clock must never be faster than the system frequency divided by 2. So, with a 25MHz
system frequency, the maximum BRGOx output clock rate is 12.5MHz. You must program
the UART to 16 oversampling when using a serial communication controller in UART
mode. On the MPC823, 8 and 32 options are also available. Assuming 16 oversampling
is chosen in the UART, a data rate of 25MHz 16 = 1.5625Mb/sec is the maximum possible
UART speed. Putting this together, the following formula must be used to calculate the bit
rate based on a particular baud rate generator configuration for a UART:
The following table lists typical bit rates of asynchronous communication. The internal clock
rate is assumed to be 16 the baud rate.
NOTE: All values are decimal.
RATES
115200
BAUD
19200
38400
57600
1200
2400
4800
9600
async baud rate = (BRGCLK, CLK2 or CLK4)
150
300
600
50
75
Table 16-23. Typical Baud Rates of Asynchronous Communication
DIV16
1
1
1
1
0
0
0
0
0
0
0
0
0
1561
1040
2082
1040
DIV
520
259
520
259
129
64
32
21
10
20
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FREQUENCY
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depending on the DIV16 bit)
RDCR and TDCR fields in the GSMR_L register).
ACTUAL
149.954
113636
300.48
600.09
1200.7
2399.2
4807.7
9615.4
19231
37879
56818
50.02
75.05
MPC823 REFERENCE MANUAL
MPC823 SYSTEM FREQUENCY (MHz)
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DIV16
1
1
1
1
0
0
0
0
0
0
0
0
0
1952
1301
2603
1301
DIV
650
324
650
324
162
80
40
26
13
25
FREQUENCY
ACTUAL
4807.69
111607
2400.1
9585.9
19290
38109
57870
300.5
1200
150
600
50
75
(clock divider + 1)
(8, 16, or 32 according to the
Communication Processor Module
DIV16
1
1
1
1
0
0
0
0
0
0
0
0
0
1919
1279
2559
1279
DIV
639
319
639
319
159
79
39
26
12
24.5760
FREQUENCY
(1 or 16
ACTUAL
118154
19200
38400
56889
1200
2400
4800
9600
150
300
600
50
75
16-159