Prescaler; Frequency Multiplier - Renesas M16C Series User Manual

M30240 Group
(5) After waiting the time required for supplying approximately 3.3V to the EXTCAP terminal, the USB
clock enable bit should be set to "1." The wait time then is (C+1)ms (the C is the capacity (
condenser that is connected to the EXTCAP terminal).
(6) After enabling the USB clock and waiting four cycles of the
be set to "1."

3.1.4.3 Prescaler

Clock f(X ) is prescaled down by the frequency synthesizer prescaler register (FSP) to generate f
IN
When the frequency synthesizer prescaler register is set at 255, the prescaler is disabled and f
f(X ). Table 3.2 shows some examples of how the frequency synthesizer prescaler register is set.
IN
f = f(X ) / 2(n+1) n: FSP value
PIN IN
Table 3.2: Example of Setting the Frequency Synthesizer Prescaler Register (FSP)
f
PIN
12 MHz
1 MHz
2 MHz
3 MHz
6 MHz

3.1.4.4 Frequency Multiplier

Clock f is a multiplied version of clock f
VCO
tiply register (FSM). When the Frequency Multiply register is set to 255, multiplication is disabled and
f = f . The value of n should be set so that f
VCO PIN
ples of how the frequency synthesizer multiply register is set.
f = f X 2(n+1) n: FSM value
VCO PIN
Table 3.3: Example of Setting the Frequency Multiply Register (FSM)
f
PIN
1 MHz
2 MHz
4 MHz
6 MHz
12 MHz
Rev.1.00 Sep 24, 2003 Page 291 of 360
Note: The value of f
FSP
Decimal List
255
5
2
1
0
. f is generated via the Frequency Synthesizer Mul-
PIN VCO
becomes 48MHz. Table 3.3 shows some exam-
VCO
FSM
Decimal List
33
11
5
3
1
φ
or greater, the USB enable bit should
should not be set below 1 MHz.
PIN
Hexadecimal List
FF
16
05
16
02
16
01
16
00
16
Hexadecimal List
4A
16
0B
16
05
16
03
16
01
16
Frequency Synthesizer
µ
F) of the
.
PIN
=
PIN
f(X )
IN
12.00 MHz
12.00 MHz
12.00 MHz
12.00 MHz
12.00 MHz
f
VCO
48.00 MHz
48.00 MHz
48.00 MHz
48.00 MHz
48.00 MHz