Asynchronous Serial Ports (UARTs)
13-18
Am186™CC/CH/CU Microcontrollers User’s Manual
or equal to threshold 1 and greater than threshold 0 selects the divisor 1 value, and so on.
A value greater than threshold 3 uses the calculated divisor value. If the registers are not
programmed (are in reset state), the High-Speed UART uses the autobaud calculated baud
divisor value. Figure 13-9 illustrates this concept.
Table 13-4 shows two examples of using the autobaud registers to enhance autobaud
detection.
Figure 13-9
Autobaud Enhancement
In autobaud mode, the receiver determines a value for the baud divisor register based on
the sampled duration of the start bit. The start bit duration in clocks is converted to a value
to be written to the baud divisor register by dividing by 16, as shown in “Programming the
Baud Rate” on page 13-15.
The configuration in example A does not support a baud rate of 57600 since this baud rate
is not represented in the table and requires a baud divisor less than that programmed in
HSPAB3. In general, any baud divisor below the maximum divisor programmed in the
Table 13-4
Examples of Autobaud Enhancement
Range
Example Register
ABDIV
ABTHRSH
Baud
Rate
# of Clocks in
Start Bit
Baud Divisors
A) @24MHz
HSPAB3
9Ch
A0h
9600
810h–A0Fh
81h–A0h
HSPAB2
4Eh
80h
19200
350h–80Fh
35h–80h
HSPAB1
27h
35h
38400
190h–34Fh
19h–34h
HSPAB0
0Dh
18h
115200
010h–18Fh
01h–18h
B) @48MHz
HSPAB3
34h
32h
57600
310h–32Fh
31h–32h
HSPAB2
1Ah
30h
115200
190h–30Fh
19h–30h
HSPAB1
0Dh
18h
230400
010h–18Fh
01h–18h
HSPAB0
00h
00h
ABDIV0
ABTHRSH0
ABTHRSH1
ABTHRSH2
ABTHRSH3
ABDIV1
ABDIV2
ABDIV3
smallest number programmed
largest number programmed
Calc. Divisor
Summary of Contents for Am186 CC
Page 1: ...Am186 CC CH CU Microcontrollers User s Manual Order 21914B...
Page 4: ...iv Am186 CC CH CU Microcontrollers User s Manual...
Page 18: ...Table of Contents xviii Am186 CC CH CU Microcontrollers User s Manual...
Page 24: ...Introduction xxiv Am186 CC CH CU Microcontrollers User s Manual...
Page 40: ...Architectural Overview 1 16 Am186 CC CH CU Microcontrollers User s Manual...
Page 86: ...System Overview 3 36 Am186 CC CH CU Microcontrollers User s Manual...
Page 92: ...Emulator Support 4 6 Am186 CC CH CU Microcontrollers User s Manual...
Page 112: ...DRAM Controller 6 8 Am186 CC CH CU Microcontrollers User s Manual...
Page 134: ...Interrupts 7 22 Am186 CC CH CU Microcontrollers User s Manual...
Page 186: ...Programmable I O Signals 9 8 Am186 CC CH CU Microcontrollers User s Manual...
Page 200: ...Watchdog Timer 11 6 Am186 CC CH CU Microcontrollers User s Manual...
Page 232: ...Asynchronous Serial Ports UARTs 13 24 Am186 CC CH CU Microcontrollers User s Manual...
Page 242: ...Synchronous Serial Port SSI 14 10 Am186 CC CH CU Microcontrollers User s Manual...
Page 264: ...High Level Data Link Control HDLC 15 22 Am186 CC CH CU Microcontrollers User s Manual...
Page 332: ...Universal Serial Bus USB 18 34 Am186 CC CH CU Microcontrollers User s Manual...
Page 348: ...Register Summary A 16 Am186 CC CH CU Microcontrollers User s Manual...
Page 376: ...Index Index 18 Am186 CC CH CU Microcontrollers User s Manual...