MB90351ASPMC1 datasheet(23/83 Pages) CYPRESS

23 / 83 page

Document Number: 002-07872 Rev. *A

Page 23 of 83

MB90350 Series

9.3 Using external clock

To use external clock, drive the X0 pin and leave X1 pin open.

9.4 Precautions for when not using a sub clock signal

If you do not connect pins X0A and X1A to an oscillator, use pull-down handling on the X0A pin, and leave the X1A pin open.

9.5 Notes on during operation of PLL clock mode

If the PLL clock mode is selected, the microcontroller attempts 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.

9.6 Power supply pins (VCC/VSS)

■ If there are multiple VCC and VSS pins, from the point of view of device design, pins to be of the same potential are connected inside

of the device to prevent such malfunctioning as latch up.

To reduce unnecessary radiation, prevent malfunctioning of the strobe signal due to the rise of ground level, and observe the standard

for total output current, be sure to connect the VCC and VSS pins to the power supply and ground externally.

Connect VCC and VSS pins to the device from the current supply source at a low impedance.

■ As a measure against power supply noise, connect a capacitor of about 0.1 μF as a bypass capacitor between VCC and VSS pins

in the vicinity of VCC and VSS pins of the device.

9.7 Pull-up/down resistors

The MB90350 series does not support internal pull-up/down resistors (Port 0 to Port 3: built-in pull-up resistors). Use external compo-

nents where needed.

9.8 Crystal Oscillator Circuit

Noises around X0 or X1 pins may be possible causes of abnormal operations. Make sure to provide bypass capacitors via shortest

distance from X0, X1 pins, crystal oscillator (or ceramic resonator) and ground lines, and make sure, to the utmost effort, that lines of

oscillation circuit do not cross the lines of other circuits.

It is highly recommended to provide a printed circuit board artwork surrounding X0 and X1 pins with a ground area for stabilizing the

operation.

Please ask the crystal maker to evaluate the oscillational characteristics of the crystal and this device.

MB90350 Series

Open

Vcc

Vss

Vcc

Vss

Vcc

MB90350

Series

Vcc

Vss

Vcc

Vss

MB90351ASPMC1 Datasheet(PDF) 23 Page - Cypress Semiconductor