Re: [N8VEM: 15616]

[Sergey <skis...@gmail.com>]

That is very similar multimeter to one I have. Yes, the frequency (Hz)
and duty cycle (%) measurements can be useful to detect pulses.
It looks like your multimeter can measure frequency of up to 5 MHz.
Which is should be more than enough for measuring signals on a 4 MHz
(or a 1.8432 MHz) clocked Z80. You can test it first by measuring
frequency on Z80 CLK input (pin 6). When you can try measuring
frequency on A0 and /MREQ. If I remember correctly /MREQ frequency
will be about 1/4 of the CLK frequency, and A0 is about 1/8 of CLK
frequency (assuming that Z80 executing NOPs).

Sometimes you might get a 50 Hz (or 60 Hz for US and few other
countries) reading, it probably means that one of the leads is
floating / not connected, or a device under test has a pin in high
impedance state. This reading is the mains frequency that is received
by the multimeter leads :-)

Thanks,
Sergey

On Feb 18, 10:37 am, rbruinsma <rbma...@gmail.com> wrote:
> No pulse on A0 and MREQ with my probe.
>
> I do have a cheap probe, I think that might be a problem also?
>
> I do have a multimeter which can read the Hz. Is that of any use for
> reading the pulse?
>
> This is the URL to my multimeter:http://www.extech.com/instruments/product.asp?catid=49&prodid=296
>
> Op maandag 18 februari 2013 08:17:31 UTC+1 schreef Sergey het volgende:
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> > Good, now you can continue with troubleshooting :-)
>
> > Can you please test A0 and /MREQ for pulses?
>
> > Thanks,
> > Sergey