Power supply noise generated transiently during the ON/OFF switching of the target power supply
(such as DC 12V supplied from a regulated power supply to the target board being programmed)
may cause the programmer to malfunction.
*Since the target interface and the programmer's internal power supply are not isolated,
noise generated on the target power supply's GND line can be transmitted directly to the programmer's
internal power supply, potentially causing the programmer to malfunction.
(Large voltage fluctuations may also cause the internal circuitry to reset and the programmer to restart.)
Factors that generate power supply noise include situations where the positive (12V, etc.) and
negative (GND) sides of the power supply are simultaneously controlled by a relay,
or when a mechanical relay that experiences chattering during power ON/OFF is used.
In this case, the solution is to either keep the GND side of the target power supply permanently
connected without relay control, or to turn on the GND relay first, followed by the positive side
with a time delay.
Also, instead of using noisy mechanical relays, use noise-free semiconductor relays (such as
photoMOS relays), or control the power ON/OFF using the remote control function supported
by the stabilized power supply unit without using relays.