Beta Disc

Here I have on my hands two identical circuits of the Beta disk interface. I want
to hang it on my spec.
Everything is clear, except for one thing, what is this signal on the main connector?
In one diagram it is designated as “INP OUT”, and in the other it is illegible, but
looks like “OUT IORQ”
The contact on the connector is designated as A2.

Please tell me where it is on the spec hangs himself.

Thanks!

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RG> CORRECTION:
RG> in the first diagram it is designated as “INP LOCK”.

There is a suspicion that this is a signal for blocking access to ports.
The essence is this: in the subject, some input/output ports overlap
with the main (and additional) ones ports of Speck himself.
And this is how it’s done: when the ROM of the subject is active, then Speck is issued
a blocking signal, in which all Speck’s ports are blocked.
But the #FE port should not be blocked (both for input and output).
Otherwise TR-DOS border will not be able to change :)
Yes, and keyboard may be needed (although unlikely ;)

How to implement: if in your Speck circuit and the port decoder there is a free
blocking input - go there.
If not, then here it is:

330 Ohm
Z80 IORQ ───█████─── IORCEQ

All Speck ports work through IORCEQ, and you feed IORQ into the subject.

Your blocking signal:
when there is no blocking, there is nothing at the output!
When there is blocking, the output is logical "1".
And you apply blocking to IORCEQ
(For this, IMHO, one transistor is enough).

Or assemble a blocking circuit on one element 2OR.

Aleksandr

01 Jul 02 10:12, Roman Gurov wrote to All:

RG> Here I have two identical circuits of the Beta disk interface. I want
RG> to hang it on my spec.
RG> Everything is clear, except for one thing, what kind of signal is this on the main connector?
RG> In one diagram it is designated as “INP OUT”, and in the other it is illegible,
RG> but it looks like “OUT IORQ”. The contact on the connector is designated as A2.
RG> Please tell me where it is is hung on the spec.

The IORQ signal from the processor goes to the controller, and is cut off from the spec circuit.
The "OUT IORQ" signal goes to the Spectrum circuit instead of the cut off IORQ.

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>
> >> Everything is clear, except for one thing, what is this signal on the main connector?
> >> In one diagram it is designated as “INP OUT”, and in the other it is illegible,
> >> but it looks like “OUT IORQ”
>
> RG> CORRECTION:
> RG> in the first diagram it is like "INP LOCK" is designated.
>
> There is a suspicion that this is a signal for blocking access to ports.
> The essence is this: in the subject, some input/output ports overlap
> with the main (and additional) ports of Speck itself.
> And this is how it is done: when the ROM of the subject is active, then Speck is issued
> a blocking signal, during which all ports of Speck are blocked.
> Well, maybe the #FE port should not be blocked (both for input and output).
> Otherwise, TR-DOS will not be able to change the border :)
> And the keyboard may be needed (although unlikely ;)
>

RG> If this output is also connected to IORQ, then what is the point of separating them
RG> and putting them in the same place? It would be possible to immediately combine
RG> in the circuit.

A resistor separates them.

RG> But according to the diagram there is already a connection to IORQ.
RG> If this output is also connected to IORQ, then what is the point of separating them
RG> and putting them in the same place? It would be possible to immediately combine
RG> in the circuit.

RG> It’s not clear.

Here it is:
330 Ohm
IORQ ───█████──┬─ IORCEQ
BLK IO─────────┘

same as this:
┌───┐
IQRQ ──┤1 ├──IOCEQ
BLK IO──┤ │
└───┘

only performed on one resistor and does not require the 2OR element
When the BLK IO output (blocking IO) is set to “1”, then
the IOCEQ pin is also set to “1”.
And the ports that are activated via IOCEQ, are blocked.

Only you need to check what exactly you have at your INP LOCK output.
It can be like a ready-made IOCEQ, then you tear it off from the IQRQ circuit,
send it only to the subject, and INP LOCK - in its place.
Or maybe it’s just a port blocking signal - then you collect
the above.

Aleksandr

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