mcf5307cft90b Freescale Semiconductor, Inc, mcf5307cft90b Datasheet - Page 328

• Manufacturer Part Number: mcf5307cft90b
• Description: Mcf5307 Coldfire Integrated Microprocessor User
• Manufacturer: Freescale Semiconductor, Inc

Operation
14.5 Operation
This section describes operation of the clock source generator, transmitter, and receiver.
14.5.1 Transmitter/Receiver Clock Source
BCLKO serves as the basic timing reference for the clock source generator logic, which
consists of a clock generator and a programmable 16-bit divider dedicated to the UART.
The clock generator cannot produce standard baud rates if BCLKO is used, so the 16-bit
divider should be used.
14.5.1.1 Programmable Divider
As Figure 14-19 shows, the UART transmitter and receiver can use the following clock
sources:
The choice of TIN or BCLKO is programmed in the UCSR.
14-18
• An external clock signal on the TIN pin that can be divided by 16. When not divided,
• BCLKO supplies an asynchronous clock source that is divided by 32 and then
TIN provides a synchronous clock mode; when divided by 16, it is asynchronous.
divided by the 16-bit value programmed in UDUn and UDLn. See Section 14.3.11,
“UART Divider Upper/Lower Registers (UDUn/UDLn).”
BCLKO
TOUT
RxD
TxD
TIN
If TIN is a clocking source for either the timer or UART, the
timer module cannot use TIN for timer capture.
Figure 14-19. Clocking Source Diagram
Freescale Semiconductor, Inc.
Rx Buffer
Tx Buffer
For More Information On This Product,
Rx
Tx
Timer Module
On-Chip
Go to: www.freescale.com
MCF5307 User’s Manual
Clocking sources programmed in UCSR
NOTE:
Generator
Prescaler
Prescaler
Clock
x16
x1
UART
TIN
TIN
Divider
16-Bit
Prescaler
x32