![](http://datasheet.mmic.net.cn/290000/XPC801ZP25_datasheet_16187868/XPC801ZP25_379.png)
Serial Communication Modules
16-8
MPC801 USER’S MANUAL
MOTOROLA
16
16.2.1.3 THE BAUD RATE GENERATOR.
the transmitter and receiver blocks. It consists of a prescaler that divides the clock source
by any integer between 2 and 64. The output of the prescaler is then further divided by a 2
divider. Eight taps are available at 1, 2, 4, 8, 16, 32, 64, and 128. The selected tap is the 16
clock for the receiver. This clock is even further divided by 16 to provide the 50% duty-cycle
1
×
clock to the transmitter.
The baud rate generator provides bit clocks to
n
×
The baud rate generator has enough flexibility to provide almost any standard baud rate
from a variety of clock frequencies. The baud rate generator is flexible in that its master clock
source can be the baud rate generator clock or it can be provided by the GPIO pin. By
configuring the proper bit in port B as an input and setting the baud source bit to 1, the baud
rate generator can be driven by an external signal. For synchronous applications, the GPIO
pin can also be configured as an input or output for the 1
×
bit clock.
16.2.1.4 THE GLOBAL CONTROLLER INTERFACE.
contains the baud control register and the control register, as well as all global logic. The
interrupt line is the logical-OR of the eight interrupt sources. The interrupt level that is sent
to the PowerPC core is user programmable. When the UARTEN bit is low, the master clock
is disabled. In this mode, power consumption is reduced to a minimum.
The global controller interface
16.2.1.4.1 Control Register.
controller and it resets to $0000.
This register controls the overall operation of the UART
UARTEN—UART Enable
This bit enables the UART controller. When it is low, the UART controller is disabled and in
low-power mode. When it is high, the UART is active.
0 = The UART controller is disabled.
1 = The UART controller is enabled.
NOTE
The status bits of the baud control, receiver, and transmitter
registers are not valid unless the UARTEN bit is set.
RXEN—RX Enable
This bit enables the receiver block. When this bit is low, the receiver is disabled and the
receive FIFO is flushed.
0 = Receiver is disabled and receive FIFO is flushed.
1 = Receiver is enabled.
CONTROL
0
1
2
3
4
5
6
7
8
9
10
RX
FUEN
11
RX
HAEN
12
RX
13
TX
14
TX
HAEN
15
TX
AVEN
UART
EN
RX EN
TX EN
RXCLK
CONT
PEN
ODE
SL
CL
GPIO
DEEN
CTS
DEEN
RDYEN
EMEN
RESET VALUE: $0000