Fujitsu MB90390 Series Hardware Manual page 139

Table 6.3-1 Function of Each Bit of the Clock Modulator Control Register (2/3)
Bit name
FMOD RUN:
Modulator status
bit2 in frequency
modulation mode
bit
"0": MCU is running with unmodulated or phase modulated clock
"1": MCU is running with frequency modulated clock
• FMODRUN indicates the status of the modulator output clock in frequency
modulation mode (FMOD=1). If the output clock is frequency modulated,
FMODRUN is set to "1", otherwise FMODRUN is set to "0".
• FMODRUN does not indicate a phase modulated clock (PMOD=1). If the modulator
is enabled in phase modulation mode, FMODRUN is set to "0".
• After enabling the frequency modulation mode by setting FMOD to "1", the
modulator is calibrated. During this time, the clock is unmodulated. Therefore it
takes several μs before the output clock switches to modulated clock and the
FMODRUN bit is set to "1". The calibration time depends on the frequency of the
oscillator (refer to the table).
Oscillator
Calibration time
Fc
64.00 μs
4 MHz
51.20 μs
5 MHz
42.67 μs
6 MHz
calibration time = 256/Fc
• During normal operation, after calibration is finished, the clock is not switched to
unmodulated clock anymore.
• Due to the synchronization of the FMOD signal and the synchronized switching to
unmodulated clock, it takes less than 9 × T0 (input clock period) before FMODRUN
changes to "0" and the clock switches to unmodulated clock after the modulator is
disabled.
• The FMODRUN bit is read only. Writing to FMODRUN has no effect.
• Before changing the parameter register CMPR, the modulator must be disabled →
FMOD=0 and FMODRUN=0.
CHAPTER 6 CLOCK MODULATOR
Function
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