DS07-16303-3E Datasheet, PDF (15/97 Pages) Fujitsu Component Limited. – 32-bit RISC Microcontroller CMOS FR30 Series

MB91121
• Crystal Oscillator Circuit
Noises around X0 and X1 pins may cause malfunctions of MB91121. In designing the PC board, layout X0, X1
and crystal oscillator (or ceramic oscillator) and bypass capacitor for grounding as close as possible.
It is strongly recommended to design PC board so that X1 and X0 pins are surrounded by grounding area for
stable operation.
• Treatment of N.C. Pins
Make sure to leave N.C. pins open.
• Mode Setting Pins (MD0 to MD3)
Connect mode setting pins (MD0 to MD3) directly to VCC or VSS.
Arrange each mode setting pin and VCC or VSS patterns on the printed circuit board as close as possible and
make the impedance between them minimal to prevent mistaken entrance to the test mode caused by noises.
• Turning on the Power Supply
When turning on the power supply, never fail to start from setting the RST pin to “L” level. And after the power
supply voltage goes to VCC level, at least after ensuring the time for 5 machine cycle, then set to “H” level.
• Pin Condition at Turning on the Power Supply
The pin condition at turning on the power supply is unstable. The circuit starts being initialized after turning on
the power supply and then starting oscillation and then the operation becomes stable.
• Source Oscillation Input at Turning on the Power Supply
At turning on the power supply, never fail to input the clock before cancellation of the oscillation stabilizing waiting.
• The device contains registers which are initialized only at a power-on reset. When it is expected to initialize
them, recycle the power to execute a power-on reset.
• Even when the A/D converter is not used, make the connections : AVCC = VCC, AVSS = VSS.
• Caution on operations during PLL clock mode
If the PLL clock mode is selected, the microcontroller attempt to be working with the self-oscillating circuit even
when there is no external oscillator or external clock input is stopped. Performance of this operation, however,
cannot be guaranteed.
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