... , or Z80 with a bad M1 line.

... /> Is bad CPU (may be M1 line) or bad contacts on system ...

... the possibility of a bad M1 line, or bad contacts on the ... board that would test the M1 line, but it would probably be ...

Yes, I am inclined to think that the Z80 in my TC2068 has a skeleton in the closet. Anyone can point me to a reliable source of Z80s with a good M1 line? The one I have is a Z8400APS from Zilog.

/Pedro

... replace CPU

Damaged M1 line causes problems with Divide (it ...

... /> I had a problem with !M1 line on my Spectrum +3 issue ... the circuit this meant that !M1 was being held low (grounded ... if they have a similar !M1 hookup your problem might lie ...

...
Basically, the Z80's M1 line doesn't function for reasons ... to have a non-functioning M1 line (in other words, it ... a machine with a faulty M1 line (since M1 signals an instruction fetch ... detect the instruction fetch without M1 working).

The ...

... under the impression that the M1 line from some batches of the ...

... put on an oscilloscope the M1 line level simply doesn't change ...

... to know is if the M1 problem is the same as ... not suffer from a bad M1 line or bad fanout.

M1 signal by adding a transistor ...

... the Z80 with a working M1 line. I have a TC2068 that ... is that of a bad M1 line.

Zetr0 mentioned the ... TC2068 board schematics and the M1 line on the cpu goes directly ...

I have a z80 which I think has the bad M1 line issue, I had to swap it to get my Disciple working on a 48k+. If someone wants to decap it and check this theory that is cool with me.

... I think has the bad M1 line issue, I had to swap ... this specific problem with the M1 line: if it's easy to ...

... this specific problem with the M1 line: if it's easy to ... I have always assumed that M1 got easily destroyed by having ...

... line and M1 being adjacent, I've killed a Z80 M1 line ... just like that (ironically, while testing the M1! ... shorted the 12V to M1. The Z80 continued to ... work minus the M1, and the attached Spectranet ... wonder: were the faulty M1 lines caused by some ...

Zilog and 'the others' should have made the M1 line dummy proof ;)

... to have a non-functioning M1 line (in other words, it's ...

... . They'd have known the M1 line would be required pretty much ...

... idea.

If the M1 functionality wasn't tested but ... a short wiping out the M1 line on every machine that went ...

Replaced the Z80 cpu on my TC2068 with the one Ben sent me. It fixed the problem with the Divide. The bad M1 line issue might not be limited to Sinclair machines.

/Pedro

... it connected to probe the M1 line. I saw something similar to ...

@Winston

Its good to see a scope description on the M1 line, and for me atleast proves that these chips are broken by either build or design.

my thanks for researching and sharing this info.

The pics by Winston show what I see when I measure the M1 line on Z80s that seem to be incompatible with the DivIDE.

I must have misunderstood. What do you mean by a "dodgy M1 line"?

I haven't done much with Z80s for years but Zilogs were the originals rather than the clones and therefore more likely to work to spec.

... I've seen have dodgy M1 lines.[/QUOTE]
That is ... (and perhaps about how easy /M1 line is damaged in Sinclair Spectrums ... , Sharp), and whenever I used /M1 signal in a circuit, that ... few cases where I used /M1 signal, it was needed otherwise ...

... (and perhaps about how easy /M1 line is damaged in Sinclair Spectrums ... Sharp), and whenever I used /M1 signal in a circuit, that ... few cases where I used /M1 signal, it was needed otherwise ... I said a "dodgy" M1 line, not a "broken" M1 line.

Calling ...

... ] no activity at all on /M1 line, even in a system where ... /M1 isn't used).

" ...

... a "dodgy" M1 line, not a "broken" M1 line[/QUOTE]
The !M1 line is either ...

... thing as a "dodgy M1 line", they either work completely ... DR version: Looks like M1 is internally disconnected in the ... t even resemble a valid M1 signal).

M1) but doesn't work ... it's loading the M1 line by marginally too much, ...

... 't notice even if the M1 line is a bit squiff (another ...