UPD75212ACW データシートの表示（PDF） - NEC => Renesas Technology

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UPD75212ACW

4-BIT SINGLE-CHIP MICROCOMPUTER

NEC => Renesas Technology 

µPD75212A

3.5 P00/INT4 PIN AND RESET PIN OPERATING PRECAUTIONS

P00/INT4 and RESET pins have the function (especially for IC test) to test µPD75212A internal operations in

addition to the functions described in sections 3.1 and 3.2.

The test mode is set when a voltage larger than VDD is applied to one of these pins. If noise larger than VDD is

applied in normal operation, the test mode may be set thereby adversely affecting normal operation.

Since there is a display output pin having a high-voltage amplitude (35 V) next to the P00/INT4 and RESET pins,

if cables for the related signals are routed in parallel, wiring noise larger than VDD may be applied to the P00/INT4

and RESET pins causing errors.

Thus, carry out wiring so that wiring noise can be minimized, If noise still cannot be suppressed, take the measure

against noise using the following external components.

• Connect diode with small VF (0.3 V or less) between • Connect a capacitor between the pins and VDD.

VDD and P00/INT4, RESET

VDD

VDD

VDD

VDD

P00/INT4, RESET

P00/INT4, RESET

3.6 XT1, XT2 AND P50 PIN OPERATING PRECAUTIONS

When selecting the 32.768 kHz subsystem clock connected to the XT1 and XT2 pins as the watch timer source

clock, the signal to be input or output to the P50 pin next to the XT2 pin must be a signal required to be switched

between high and low the minimum number of times (once or less per second).

If the P50 pin signal is switched frequently between high and low, a spike is generated in the XT2 pin because

of capacitance coupling of the P50 and XT2 pins and the correct watch functions cannot be achieved (the watch

becomes fast).

If it is necessary to allow the P50 pin signal to switch between high and low, mount an external capacitor to the

P50 pin as shown below.

µPD75212A

P50

XT1

XT2

32.768 kHz

0.0068 µ F

13

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