MB91245_07 Datasheet, PDF (17/84 Pages) Fujitsu Component Limited. – 32-bit Microcontroller

MB91245/S Series
• Crystal oscillator circuit
Noise near the X0/X1 pins and X0A/X1A pins may cause the device to malfunction. Design the PC board such
that X0/X1 pins, X0A/X1A pins, the crystal oscillator (or ceramic oscillator), and the bypass capacitor to the
ground are placed as near one another as possible. When routing the X0 and X1 signals, they should be shielded
for use on the board. Caution must be taken especially when using a pin next to the X0.
It is strongly recommended to design the PC board artwork with the X0, X1, X0A and X1A pins surrounded by
ground plane because stable operation can be expected with such a layout.
In addition, a sub clock is required even when a dual clock product is used as a single clock product.
When using MB91247S/248S/F248S/F249S, connect the X0A pin to GND and leave the X1A pin open.
Please ask the crystal maker to evaluate the oscillational characteristics of the crystal and this device.
• Mode pins (MOD0 to MOD2)
These pins should be connected directly to VCC or VSS pins. To prevent the device erroneously switching to test
mode due to noise, design the PC board such that the distance between the mode pins and VCC or VSS pins is
as short as possible and the connection impedance is now.
• Operation at start-up
Always use the INIT pin to perform a setting initialization reset (INIT) after power-on. Immediately after power-
on, hold the low level input to the INIT pin for the stabilization wait time required for the oscillator circuit, to take
the oscillation stabilization wait time for the oscillator circuit.
For INIT via the INIT pin, the oscillation stabilization wait time setting is initialized to the minimum value.
• Source oscillation input upon power-on
When power-on, always input the clock for the duration of the oscillation stabilization delay time.
• Treatment of power supply pins on A/D converter
Connect to ensure “AVCC = AVRH = VCC and AVSS = VSS” even if the A/D converter is not in use.
• Power-on sequence for power supply analog input of A/D converter
Always supply power to the A/D converter (AVCC and AVRH) and apply analog input (AN0 to AN 31) after turning
on the digital power supply (VCC). Also, turn off the power supply for the A/D converter and analog input before
turning off the digital power supply (VCC). In so doing, the power supply must be turn on and off so that AVRH
does not exceed AVCC. Even when using a pin shared with analog input as an input port, ensure that the input
voltage does not exceed AVCC (There is no problem in turning on or off the analog and digital power supplies at
the same time).
• Handling of power supply for high-current output buffer pin (DVCC, DVSS)
Always apply power to high-current output buffer pins (DVCC) after turning on the digital power supply (VCC). In
addition, turn off the power supply for the high-current output buffer pins before turning off the digital power
supply (VCC).
Apply the same power as for high-current output buffer pins even when using such pins as general-purpose
ports (There is no problem in turning on or off the power supply for the high-current output buffer pins and the
digital power supply at the same time).
Always use the GND pin (DVSS) for the high-current output buffer pin at the same potential as the digital GND (VSS).
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