15
MB90F243H
5. Crystal Oscillation Circuit
Noise in the vicinity of the X0 and X1 pins will cause this device to operate incorrectly. Design the printed circuit
board so that the bypass capacitor connecting X0 and X1 pins and the crystal oscillator (or ceramic oscillator)
to ground is located as close to the device as possible.
In addition, because printed circuit board artwork in which the area around the X0 and X1 pins is surrounded
by ground provides stable operation, such an arrangement is strongly recommended.
6. Sequence for Applying the A/D Converter Power Supply and the Analog Inputs
Always be sure to apply the digital power supply (VCC) before applying the A/D converter power supply (AVCC,
AVRH, and AVRL) and the analog inputs (AN0 to AN7).
In addition, when the power is turned off, turn off the A/D converter power supply and the analog inputs first,
and then turn off the digital power supply. (Turning on or off the analog and digital power supplies simultaneously
will not cause any problems.)
Whether applying or cutting off the power, be certain that AVRH does not exceed AVCC.
7. External Reset Input
To reliably reset the controller by inputting an “L” level to the RST pin, ensure that the “L” level is applied for at
least five machine cycles.
8. HST Pin
When turning on the system, be sure to set the HST pin to “H” level. Never set the HST pin to “L” level while the
RST pin is in “L” level.
9. CLK Pin
CLK
X0
X1
To internal blocks
ex. 40 MHz
CLK pin cannot use as I/O port.
Care must be taken that this is different from standard specification for F MC-16F family.
Note:
STOP
Divide by 2 circuit
2
STOP