Baud Rate By Dedicated Baud Rate Generator - Fujitsu MB90895 Series Hardware Manual

14.5.1

Baud rate by dedicated baud rate generator

The baud rate that can be set when the output clock of the dedicated baud rate
generator is selected as the transfer clock of the UART0 is shown.
I Baud rate by dedicated baud rate generator
The baud rate based on the dedicated baud rate generator is set by setting the clock input source select bits
(SMR0: CS2 to CS0) to "000
When generating a transmission/reception clock signal using the dedicated baud rate generator, the
machine clock frequency is divided by the communication prescaler and then the divide ratio for the clock
input source selected by the clock selector is selected to determine the baud rate.
The division ratio at which the machine clock frequency is divided by the communication prescaler is the
same for the clock synchronous and asynchronous modes. The division ratio at which the baud rate is
determined is different for the clock synchronous and asynchronous modes.
Figure 14.5-2 shows the baud rate selector based on the dedicated baud rate generator.
Figure 14.5-2 Baud Rate Selector Based on Dedicated Baud Rate Generator
Communication prescaler
CDCR0 MD0 DIV3
: Machine clock frequency
G
Calculation expression for baud rate
Baud rate in asynchronous mode = φx div x (division ratio of transfer clock in asynchronous mode)
Baud rate in clock synchronous mode = φx div x (division ratio of transfer clock in clock synchronous
mode)
φ:Machine clock
div: Division ratio based on communication prescaler
" to "100
B
/3 /4
/5 /6
/8
DIV0
".
B
SMR0 CS2 CS0
(Clock input source select bit)
Clock selector
Division circuit
Clock sync
Select from 1/2,1/4,
1/8,1/16 or 1/32
Asynchronous
Select internal fixed
division ratio
SMR0 MD1 MD0
(Operating mode select bit)
CHAPTER 14 UART0
Baud rate
407