Asynchronous Serial Ports (UARTs)
13-14
Am186™CC/CH/CU Microcontrollers User’s Manual
Figure 13-4 illustrates the behavior of the RTR_U signal. Figure 13-5 illustrates the behavior
of the RTR_U signal with the FIFO. Note that the RTR_U signal is deasserted as soon as
the serial port begins receiving a character and is reasserted when the data is read from
the receive data register.
Figure 13-4
RTR_U Signal Behavior
Figure 13-5
RTR_HU Signal Behavior with Receive FIFOs
13.5.5
Clock Sources and Baud Rate
The UARTs have two possible clock sources, the processor clock or the UCLK input signal.
The possible clock configurations are shown graphically in Figure 13-6. The XTRN bit in
the (H)SPCON1 register selects the clock source.
The baud clock is generated by dividing the clock source by the value of the Baud Rate
Divisor ((H)SPBDV) register. In addition, the High-Speed UART supports automatic baud
rate detection. The UARTs select the clock from either the CPU clock or the UCLK signal,
independent of any other settings.
In the Am186CC and Am186CU microcontrollers, the USBSOF signal must not be enabled
at the same time as UCLK.
RXD_U
RTR_U
RDR Set
RDR Set
Received Data Read
RDR Cleared
RXD_HU
RTR_HU
FIFO
byte 32
receiving byte 32
in FIFO
receiving byte 31
receiving byte 30
FIFO read
FIFO full
start bit for byte 32
CU
CC
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...