UPD75004 Datasheet, PDF (15/66 Pages) NEC – 4-BIT SINGLE-CHIP MICROCOMPUTER

µPD75004, 75006, 75008
3.6 NOTES ON USING THE P00/INT4, AND RESET PINS
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In addition to the functions described in Sections 3.1 PORT PINS and 3.2 NON PORT PINS, an exclusive
function for setting the test mode, in which the internal fuctions of the µPD75008 are tested (solely used for
IC tests), is provided to the P00/INT4 and RESET pins.
If a voltage exceeding VDD is applied to either of these pins, the µPD75008 is put into test mode. Therefore,
even when the µPD75008 is in normal operation, if noise exceeding the VDD is input into any of these pins, the
µPD75008 will enter the test mode, and this will cause problems for normal operation.
As an example, if the wiring to the P00/INT4 pin or the RESET pin is long, stray noise may be picked up
and the above montioned problem may occur.
Therefore, all wiring to these pins must be made short enough to not pick up stray noise. If noise cannot
be avoided, suppress the noise using a capacitor or diode as shown in the figure below.
• Connect a diode having a low VF across
P00/INT4 and RESET, and VDD. (0.3 V max.)
VDD
• Connect a capacitor across P00/INT4 and
RESET, and VDD.
VDD
Low VF
diode
VDD
P00/INT4, RESET
VDD
P00/INT4, RESET
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