Tape read/write on expansion port?

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mrtinb
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Tape read/write on expansion port?

Post by mrtinb » Fri Mar 30, 2018 5:03 pm

When port FF is read and written in the kernel when reading and writing tape, can it be seen on the expansion port?
Martin
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube

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Andy Rea
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Re: Tape read/write on expansion port?

Post by Andy Rea » Fri Mar 30, 2018 5:15 pm

Reading of port $FE at the expansion port is possible, external keyboards are one example.

So you need to decode port address and ~iorq and ~rd I believe tape input is bit 7. You must remember for port $FE to work correctly you use open collector drivers only.. DO NOT DRIVE DATA LINES HIGH.

So that's tape input covered... Tape output is somewhat harder...

I guess you could watch the 2 ports ( I forget which ones without looking at my notes ) and set / under a latch accordingly ( your latch should mimic the vsync pulses ) and use that as a tape out signal....

Regards Andy
6 x ZX81, 1 x TS1500 , 1 x +3e, 1 x timex 2040 printer, 1 x timex 2020 cassette deck, siclair printer and some spectrum

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Re: Tape read/write on expansion port?

Post by mrtinb » Fri Mar 30, 2018 7:28 pm

Thank you for your informative reply.
Martin
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Re: Tape read/write on expansion port?

Post by mrtinb » Fri Mar 30, 2018 9:27 pm

So wouldn't it be simple to create a little circuit with a few logic gates, that will bring the same signal as the EAR and MIC, but with 5V TTL? This would be easier to record and playback compared to the 0.01V on the MIC.
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Re: Tape read/write on expansion port?

Post by 1024MAK » Fri Mar 30, 2018 9:37 pm

The signal level on the external mic jack socket is mostly due to the resistor and capacitor network on the PCB. There is nothing to stop you connecting a short wire to the solder pin of the ULA (or ULA socket) and feeding it to a logic gate in a logic chip. Then the output of this chip can output to whatever you like. But keep in mind that you will get part of the TV signal on this signal line.

The ear input is a bit more tricky, as the levels are set by Sinclair attempting to match the levels expected from a actual cassette tape recorder. But it is possible to feed a signal (via a suitable resistor network) to the ULA pin.

Mark

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Re: Tape read/write on expansion port?

Post by mrtinb » Fri Mar 30, 2018 9:41 pm

My idea was to have a board on the expansion port with ear and mic that would be 5V TTL without opening the ZX81 and modify the board.
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Andy Rea
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Re: Tape read/write on expansion port?

Post by Andy Rea » Fri Mar 30, 2018 9:41 pm

whilst it could be done, and maybe back in the 80's it might have been a good idea, with the usb / sd card options we have for save and load why would anyone bother ?

i believe Wilf did a similar thing years ago before usb / sd card solutions for high speed serial transfer to / from a pc.

Regards Andy
6 x ZX81, 1 x TS1500 , 1 x +3e, 1 x timex 2040 printer, 1 x timex 2020 cassette deck, siclair printer and some spectrum

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Re: Tape read/write on expansion port?

Post by Moggy » Fri Mar 30, 2018 10:03 pm

Andy Rea wrote:
Fri Mar 30, 2018 9:41 pm
whilst it could be done, and maybe back in the 80's it might have been a good idea, with the usb / sd card options we have for save and load why would anyone bother ?

i believe Wilf did a similar thing years ago before usb / sd card solutions for high speed serial transfer to / from a pc.

Regards Andy
Agreed. 6 mins to load Football Manager why anyone would want to mess around with tape is beyond me, another thought exercise like the three rampack gubbins methinks. :lol:

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Re: Tape read/write on expansion port?

Post by mrtinb » Fri Mar 30, 2018 10:05 pm

I learn when I ask
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Re: Tape read/write on expansion port?

Post by mrtinb » Fri Mar 30, 2018 10:06 pm

It's for my Lambda 8300 which does not work with neither ZXpand nor ZXblast.
Martin
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube

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