Internal And External Clock - Fujitsu MB90390 Series Hardware Manual

CHAPTER 19 UART0, UART1
19.6

Internal and External Clock

Setting RC3 to RC0 to "1101
Setting RC3 to RC0 to "1111
The external clock frequency has a maximum value of 2 MHz.
■ Internal and External Clock
The CLK asynchronous baud rate is the CLK synchronous baud rate divided by 8. Also, data transfer is
possible if the CLK asynchronous baud rate is in the range -1% to +1% of the selected baud rate. Table
19.6-1 lists the baud rate and reload value. The values in this table are calculated for a machine cycle of
7.3728 MHz. However, do not use the settings marked as "-" in the table.
Baud rate=
Table 19.6-1 Baud Rate and Reload Value
Baud Rate (bps)
76800
38400
19200
9600
4800
2400
1200
600
300
The values in the table are the reload values (decimal) for reload count operation of the 16-bit Reload
Timer.
326
" selects the clock signal from the 16-bit Reload Timer.
B
" selects the external clock.
B
φ / X
[bps]
8 × 2 (n+1)
φ: Machine cycle
⎛
⎜
⎜
X: Divider ratio for the count clock source for
⎜
the internal timer
⎜
⎝
n: Reload value (decimal)
1
X = 2
(divide machine cycle by 2)
2
5
11
23
47
95
191
383
767
⎞
⎟
⎟
⎟
⎟
⎠
Reload Value
X = 2
(divide machine cycle by 8)
3
-
-
2
5
11
23
47
95
191