ZXmore or the ZX80CORE follow-up

[Andy Rea]

oh i did not know you could power it via the usb

yes i was wondering about the address decoding sound card uses $CF, $0F & $DF, $1F so not sure what is happening.

still i;m having a little fun, trying out what works and what does not

Regards Andy

[1024MAK]

Hello Karl

A couple of questions...

First question: when using a keyboard "membrane" with the smd tactile switches. Am I suppose to leave the adhesive backing tape on the keyboard "membrane" in place, or am I suppose to remove the backing tape to reveal the adhesive?

Second question: I can switch to, and between instances for the ZX81 modes okay (instances 1 to 5). Also back to the ZXmaster screen. I can also switch to the ZX80 modes, instances 6 and 7 okay. But once in a ZX80 mode, I cannot switch to any other instances. Including not being able to get back to the ZXmaster screen. The only way I can get out of a ZX80 mode, is by using the reset switch. After reset, the ZX81 instances retain their data and programs, but the ZX80 instance does not. Is this a known limitation? Or am I missing something?

Mark

[Becky]

Hello,

I've just joined the forum and did not see any 'introduce yourself' type thread, so I hope it is okay to jump straight in with a question.

In the ZXmore kit there is a bag with the resisters and diodes in it. The final item on the list is an inductor. My understanding of an inductor is that it is some kind of coil, as such I cannot identify it among the components. I can't find where it goes on the board either. Can anyone point me in the right direction please.

Thank you.
Becky.

[IanB]

Hello Becky, welcome to the forum!

(Sorry, I don't know the answer to your question though).

[Andy Rea]

Hi Becky,

Looks like a little stubby resistor. Mine was greenish in colur and goes to the left of the regulator the board is marked L1 and has a small black rectangle.

[1024MAK]

Hello and welcome to our forum Becky

Just like other components, inductors come in big and small sizes. The smaller ones are sometimes called high frequency chokes. These do look just like a resistor.

If you have a multimeter, it is easy to tell if you are testing an inductor that looks like a resistor, because the resistance is low and does not match the colour code.

The position of the inductor on the PCB is marked "L1". It is located between IC3 and D1, D2, C2. See the picture just posted above

Mark

[PokeMon]

oh i did not know you could power it via the usb

yes i was wondering about the address decoding sound card uses $CF, $0F & $DF, $1F so not sure what is happening.

Hmmm - that is maybe the problem.
I am using a configurable address which use A0 and A1 plus one other address line (AX) to be configured with A3-A7 by user.
Unfortunately it is not configurable now (only A7 possible) - but addresses $0F and $1F would conflict now with A7.
I think this is a bit unsual as addresses are normally low active used and $0F uses four address lines low (A4A7) which give much potential of conflicts.

Not sure what really happens as I am just writing to addresses $7C-$7F while the sound interface should be passive.

[PokeMon]

Hello Karl

A couple of questions...

First question: when using a keyboard "membrane" with the smd tactile switches. Am I suppose to leave the adhesive backing tape on the keyboard "membrane" in place, or am I suppose to remove the backing tape to reveal the adhesive?

Second question: I can switch to, and between instances for the ZX81 modes okay (instances 1 to 5). Also back to the ZXmaster screen. I can also switch to the ZX80 modes, instances 6 and 7 okay. But once in a ZX80 mode, I cannot switch to any other instances. Including not being able to get back to the ZXmaster screen. The only way I can get out of a ZX80 mode, is by using the reset switch. After reset, the ZX81 instances retain their data and programs, but the ZX80 instance does not. Is this a known limitation? Or am I missing something?

Mark

Hi Mark,

you can fix the membrane in either way but I left the paper backing on the keyboard membrane while only using the both adhesive sides of the small tape around the keys. This holds quite strong and maybe give the opportunity to release the membrane easily later for some other purpose. So up to you.

The described behaviour is normal for revision 1 (0.9) as the multitasking modes are working with NMI only. This is not available when starting ZX80 and not available when releasing control with double-shift C in a ZX81 instance. The only way getting back to control is the reset. The reason why ZX80 and ZX81 programs can be lost when pressing reset is, that there is no instance information stored so nobody knows the stack pointer and other registers when simply pressing reset. So it is not possible to restore at the last point for these instances.

I am trying to solve this in the next release with a changed new NMI detection which would go a little to deep to explain now. The hard part is not to detect the NMI but the cycle where the NMI routine starts without comparing the full 16 bit address bus. So hopefully I get this working in the next release as expected which would allow other features like showing a display in ZX80 mode as well when programs running.

Karl

[PokeMon]

Thanks for the pic, Andy.
This shows exactly the resistor-like inductor - that's why it is in the resistor bag.
It has 0.120 ohm - so could be detected easily with a multimeter with connection tester.
Would be shown as zero like.

[1024MAK]

Hi Karl

Thanks for answering my questions

Mark