Strange memory expansion

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zxhenk
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Strange memory expansion

Post by zxhenk »

I have bought an Timex 1000 with a 64K ram expansion. The stange thing is it has a jack plug enry on one side and above that a 11 pin connector. Does anyone know what this is for? See attached pics.
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XavSnap
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Re: Strange memory expansion

Post by XavSnap »

Hi,
May be a Centronics printer expansion socket… (8 datas out & 3 stats in)
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siggi
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Re: Strange memory expansion

Post by siggi »

I don't see any pics.

Is it that board on the left side of the picture?

https://forum.tlienhard.com/phpBB3/view ... 866#p32866

That is a 64K ram pack, having also an 8 bit output port, e. g. for remote control of a cassette recorder and for paging of ram banks

Siggi
Last edited by siggi on Sat Oct 03, 2020 8:02 pm, edited 1 time in total.
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zxhenk
Posts: 18
Joined: Tue May 05, 2020 11:32 am

Re: Strange memory expansion

Post by zxhenk »

No that is not the same board. I try again uploading some pics. The last time they did not show for some reason.
IMG_4919.jpg
IMG_4918.jpg
IMG_4917.jpg
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XavSnap
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Re: Strange memory expansion

Post by XavSnap »

I never seen it …
64kb, an integrated power regulator, a relay.
It's not an IO interface, but perhaps a bus to connect a keyboard on the address ports, or to get joystick signals.

Pretty card…

Don't know about this logo…
logo.jpg
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siggi
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Re: Strange memory expansion

Post by siggi »

I have a board of the same (probably German) company (for an enhanced character set).

To use 64K ram, some kind of paging-logic is needed to switch different ram block to the same address area "seen" by the Z80 (e. g. 2 16kB pages at address 32K-48K). Thus an output latch (typically 8 bit) is needed to select the pages( maybe 1, 2, or 3 bits needed). The remaining bits can be used as general purpose output. If no paging is used, all 8 bit can be used for other purposes.

Probably one of those output bits drives the relay (my ram board has 2 relays). Thus external signals (e. g. the remote control of a cassette recorder) can be switched on/of by machine code OUT instructions.

A Centronics port would require much more signals: common ground, 8 data bits (out), strobe signal (output), ACK (input), busy (input), paper end (input), error (input) .... : https://de.wikipedia.org/wiki/IEEE_1284

Siggi
My ZX81 web-server: online since 2007, running since dec. 2020 using ZeddyNet hardware
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zxhenk
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Joined: Tue May 05, 2020 11:32 am

Re: Strange memory expansion

Post by zxhenk »

I have found out after some picture search on Google it is an expansion from K-tronics see this page https://k1.spdns.de/Vintage/Sinclair/80 ... 2064K-RAM/

A pitty the instruction manual is not downloadable from this page.

It must be a rare expansion because I collect zx81 stuff for over 30 years and this is the first time I came across this one.
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