Fujitsu MB90480 Series Hardware Manual page 44

CHAPTER 1 OVERVIEW OF MB90480/485 SERIES
❍ Notes on using external clock
To use external clock, drive only pin X0. Be sure to set up pin X1 to be open.
Figure 1.7-1 shows a usage of the external clock (f=25 MHz or below).
❍ Note on operations during PLL clock mode
On this microcontroller, if in case the crystal oscillator breaks off or an external reference clock
input stops while the PLL clock mode is selected, a self-oscillator circuit contained in the PLL
may continue its operation at its self-running frequency. However, Fujitsu will not guarantee
results of operations if such failure occurs.
■
Notes on handling the power supply
❍ Stabilizing the power supply
Even in the range of V
a misoperation. Fujitsu recommends that, as a reference for stabilization, the V
variation (P-P value) in the commercial frequency (50/60 MHz) must be 10% of the standard
V value or lower, or the transient variation must be 0.1 V/ms in instantaneous variation
CC
including power supply switching.
❍ To use this product as a single system
To use this product, which is two system products, as a single system, use it under the
conditions of X0A = V
❍ Writing to flash memory
For serial writing to flash memory, always make sure that the operating voltage V
3.13 V and 3.6 V.
For normal writing to flash memory, always make sure that the operating voltage V
between 3 V and 3.6 V.
❍ Note on using dual power supply
The MB90485 series usually uses 3V power supply. However, if Vcc3=3V/Vcc5=5V, P20 to
P27, P30 to P37, P40 to P47, and P70 to P77 are used as the interface of 5V power supply.
Note that analog power supply (AV
❍ Handling of P90/CS0 pin
P90/CS0 pin outputs "L" during flash serial writing. Do not input from outside.
22
Figure 1.7-1 Use of external clock
OPEN
power supply voltage, a rapid change in the power supply may cause
CC
and X1A = OPEN.
SS
, AVRH) is used only as 3V during A/D conversion.
CC
X0
X1
CC
ripple
CC
is between
is
CC