Fujitsu 8FX

MB95630H Series
MN702-00009-2v0-E FUJITSU SEMICONDUCTOR LIMITED 57
CHAPTER 3 CLOCK CONTROLLER
3.9 Operation of Prescaler
3.9 Operation of Prescaler
The prescaler generates count clock sources to different peripheral functions.
■ Operation of Prescaler
The prescaler generates count clock sources from a clock whose frequency is generated by
dividing the machine clock(MCLK),or from buffered signals from the time-base timer(F
CH
/2
7
,
F
CH
/2
8
, F
CRH
/2
6
, F
CRH
/2
7
, F
MCRPLL
/2
6
, or F
MCRPLL
/2
7
), and then supplies them to different
peripheral functions. The prescaler keeps operating while the machine clock and the clocks
from the time-base timer are being supplied.
Table 3.9-1, Table 3.9-2 and Table 3.9-3 list the count clock sources generated by the
prescaler.
Table 3.9-1 Count Clock Sources Generated by Prescaler (F
CH
)
Count clock source
frequency
Frequency
(F
CH
= 20 MHz,
MCLK = 10 MHz)
Frequency
(F
CH
= 32 MHz,
MCLK = 16 MHz)
Frequency
(F
CH
= 32.5 MHz,
MCLK = 16.25 MHz)
MCLK/2 5 MHz 8 MHz 8.125 MHz
MCLK/4 2.5 MHz 4 MHz 4.0625 MHz
MCLK/8 1.25 MHz 2 MHz 2.0313 MHz
MCLK/16 0.625 MHz 1 MHz 1.0156 MHz
MCLK/32 0.3125 MHz 0.5 MHz 0.5078 MHz
F
CH
/2
7
156.25 kHz 250 kHz 253.9 kHz
F
CH
/2
8
78.125 kHz 125 kHz 126.95 kHz
Table 3.9-2 Count Clock Sources Generated by Prescaler (F
CRH
)
Count clock source
frequency
Frequency
(F
CRH
= 4 MHz,
MCLK= 4 MHz)
MCLK/2 2 MHz
MCLK/4 1 MHz
MCLK/8 0.5 MHz
MCLK/16 0.25 MHz
MCLK/32 125 kHz
F
CRH
/2
6
62.5 kHz
F
CRH
/2
7
31.25 kHz