Please! Recommend away! Grateful for links.
EPROM suggestions
Re: EPROM suggestions
All that I've learned - https://msknight.com/bbc/index.html#zx81
Re: EPROM suggestions
https://www.ebay.de/itm/176099977330
Is the product.
I have no experience with this seller.
I normally buy at the seller
gc_supermarket (247002) which is on holidays until 16th of February
Is the product.
I have no experience with this seller.
I normally buy at the seller
gc_supermarket (247002) which is on holidays until 16th of February
In theory, there is no difference between theory and practice. But, in practice, there is.
Re: EPROM suggestions
I don't mind waiting for a known good seller. I found their shop, but a search for W27C512 turns up nothing.
All that I've learned - https://msknight.com/bbc/index.html#zx81
Re: EPROM suggestions
Drat. They've de-listed all their items while they're away. (sigh)
All that I've learned - https://msknight.com/bbc/index.html#zx81
Re: EPROM suggestions
On the other side deactivated listings during absence are a sign of good sellers
In theory, there is no difference between theory and practice. But, in practice, there is.
- 1024MAK
- Posts: 5145
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: EPROM suggestions
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
Re: EPROM suggestions
Well, this is a public forum! I don't want to get banned! Too much good advice
I did just order some of those one time chips from Farnell though, gives me something to play with and mess up.
All that I've learned - https://msknight.com/bbc/index.html#zx81
Re: EPROM suggestions
I've just noticed and registered... if I do the BIOS mod, which requires CE to be tied to ground, then that will stuff up using something like the ZXpand+ because it will want to disable the BIOS by trying to keep that line high.
Do I understand that correctly please?
Do I understand that correctly please?
All that I've learned - https://msknight.com/bbc/index.html#zx81
Re: EPROM suggestions
No need to worry.
Zxpand disables romcs which ist used with a ROM mod.
Zxpand disables romcs which ist used with a ROM mod.
In theory, there is no difference between theory and practice. But, in practice, there is.
- 1024MAK
- Posts: 5145
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: EPROM suggestions
The control signal from the ULA (/ROMCS) goes via a resistor (so that an external device can disable the ROM) to pin 22 of the ROM socket. On a 27 series EPROM, this is /OE (output enable or /G ). The EPROM will only output data if this control line is at a logic low level. Hence it does not matter if pin 20 (/CE - chip enable or /CS - chip select or /E - enable) is always low (connected to 0V/GND).
For the EPROM to drive its databus lines BOTH /OE and /CE must be at a logic low level.
When the external device (ZXpand / ZXpand+ or other device) wants to page out the internal ZX81 ROM, it takes the /ROMCS line high and the EPROM then disables all its outputs.
Mark
For the EPROM to drive its databus lines BOTH /OE and /CE must be at a logic low level.
When the external device (ZXpand / ZXpand+ or other device) wants to page out the internal ZX81 ROM, it takes the /ROMCS line high and the EPROM then disables all its outputs.
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.