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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 13th Jan 2022, 11:25 pm   #1
Phil__G
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Default Genuine DS1210 NVRAM controllers

In the current silicon climate fake chips are rife and real DS1210 NV RAM controllers have been really hard to find, with many reports from disappointed buyers. I've found a good reliable UK source of genuine Dallas chips at a reasonable price, please PM or email me & I'll pass on details if interested.

The DS1210 is a DIP8 and sits in series with the Vcc line and /CE on any CMOS static RAM, and with a tiny coin-cell turns it into a non-volatile NVRAM. This typically works out about a third of the cost of a 'commercial' NVRAM such as a 48Z08 etc.

I couldnt wait to confirm these were good, so I did a quick & dirty deadbug kluge of a DS1210 and an AS6C1008 ...sorry if this offends but it works great!
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Old 17th Jan 2022, 4:39 pm   #2
Phil__G
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Default Re: Genuine DS1210 NVRAM controllers

Just a quick update, this same source has genuine NOS Dallas DS1225 8k x 8 NVRAMs
at 12 post free, ideal for the PICLV2. Please PM or email me & I'll pass on details.
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Old 18th Jan 2022, 7:22 pm   #3
Mark1960
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Default Re: Genuine DS1210 NVRAM controllers

My own preference is to use the MAX818L, still a current part, the SOP-8 package is the cheapest option and not too difficult to hand solder. This also provides a reset circuit and the watchdog input can be used for a manual reset switch, the watchdog input has to be held low for 1.6 seconds, but this helps to avoid accidental resets.
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Old 19th Jan 2022, 7:35 pm   #4
Phil__G
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Default Re: Genuine DS1210 NVRAM controllers

The Max818LCPA is nice Mark but here in the UK it costs almost twice as much as the DS1210. Nice to have another option though
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Old 19th Jan 2022, 9:54 pm   #5
Mark1960
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Default Re: Genuine DS1210 NVRAM controllers

Were you looking at the DIL or the SOP package? DIL is too expensive here too. I use the SOP with smt adapter to DIL.
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Old 1st Feb 2022, 2:35 am   #6
Michael - K8LH
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Default Re: Genuine DS1210 NVRAM controllers

So I could use a DS1210, a 32K 2.7v-5.5v CMOS SRAM (AS6C62256 perhaps?), and a little 3.3v battery and have something that behaves like an nvRAM? That's pretty cool...

Looks like I can purchase five DS1210 ICs in DIP8 package from Chinese sources for around $4.00 (about 80 each).

Thanks for the info', Phil...

Cheerful regards...
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Old 1st Feb 2022, 7:56 am   #7
SiriusHardware
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Default Re: Genuine DS1210 NVRAM controllers

I think it's only fair to point out that Phil has found there is a big problem with fakes from many sources, hence the reason for this thread (as he had found a UK source of genuine ones).
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Old 1st Feb 2022, 5:31 pm   #8
Phil__G
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Default Re: Genuine DS1210 NVRAM controllers

Indeed, at 80 each they will almost certainly be fakes, probably repainted op-amps or 555 timers. Be aware that cosmetically they are very well faked - skimmed and laser etched with OEM logos and valid date codes so they look like new and totally convincing. There are numerous Youtube videos where a professional teardown of a variety of chips reveals anything but the original die
Cheers
Phil
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Old 1st Feb 2022, 5:39 pm   #9
Timbucus
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Default Re: Genuine DS1210 NVRAM controllers

I think I have said before this is not a new problem with fake chips - here is one from an upcoming video where I am going through ETI July 1978...

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Old 1st Feb 2022, 9:32 pm   #10
Mark1960
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Default Re: Genuine DS1210 NVRAM controllers

I think most of the suppliers of fake chips rely on you not having a way to test them and report them as fake within the return period.

I did receive a set of fake INS8060, I could verify not running in a working MK14. Although they had identical marking and datecodes on the top side, they were from completely different moulds when looking at the underside of the chip. They wanted me to pay to ship them back, another ruse to avoid returns, but the packing showed a return address here in canada so I offered to send there. Eventually they gave up and refunded.

Utsource have been mostly OK, just one set of 74AC04 that would only run at 700kHz in a 4MHz crystal oscilator, suspect they might be remarked 74C04.

Aliexpress has also yielded a few surprise bargains. Though packing is sometimes poor, for example DIL chips stacked on top of each other and wrapped in clingfilm, though the chips did seem ok.
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Old 25th Feb 2022, 12:10 pm   #11
Slothie
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Default Re: Genuine DS1210 NVRAM controllers

I've been pondering how to solve the battery backup on my Ortonview PCB and while the DS1210 would seem to be an option, the problem of fakes and the fact that the DS1210 is no longer in production is making me look for other options. I may be able to just use a MOSFET to buffer the CE signal and a diode to switch the battery but I'd prefer a different solution. The MAX818L mentioned above looks like an option but although it is available in DIP no-one seems to stock it I would probably design a dual footprint for it just to be safe. The fact is is 4 a pop isn't really an issue in the quantities I'd be using them, and the fact its available from farnell etc means sourcing a non-fake one is going to be easier.

I am however open to looking at other options.
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Old 25th Feb 2022, 1:09 pm   #12
SiriusHardware
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Default Re: Genuine DS1210 NVRAM controllers

There is the discrete component method which I mentioned way back in #137 of the OrtonView PCB thread (taken from a 1990s Maplin Z80 project). Fiddly to build on Veroboard, but just a minute or two more on a PCB and without using any exotic ICs.

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Old 25th Feb 2022, 2:27 pm   #13
Slothie
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Default Re: Genuine DS1210 NVRAM controllers

Quote:
Originally Posted by SiriusHardware View Post
There is the discrete component method which I mentioned way back in #137 of the OrtonView PCB thread (taken from a 1990s Maplin Z80 project). Fiddly to build on Veroboard, but just a minute or two more on a PCB and without using any exotic ICs.
Yes, now you mention it I do recall that, I remember at the time I couldn't quite see how it worked immediately because there was a lot going on with the diagram, but then again I think I thought I go back and look at it later, and later never happened! Perhaps that time is now.
I still haven't even tried out the noise generator! I must do that, as I want to see if I can get the "Twonky" music composer running.
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Old 25th Feb 2022, 2:43 pm   #14
SiriusHardware
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Default Re: Genuine DS1210 NVRAM controllers

You can find the whole circuit of the CPU PCB from which that detail was taken here in an issue of Maplin magazine, on magazine page 57 / PDF page 59.

https://worldradiohistory.com/UK/Map...cs-1992-10.pdf
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Old 25th Feb 2022, 2:54 pm   #15
Slothie
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Default Re: Genuine DS1210 NVRAM controllers

Quote:
Originally Posted by SiriusHardware View Post
You can find the whole circuit of the CPU PCB from which that detail was taken here in an issue of Maplin magazine, on magazine page 57 / PDF page 59.

https://worldradiohistory.com/UK/Map...cs-1992-10.pdf
Thanks, I just had a look at it and I think I can see how it works. I think if I redraw it with just the "vital" components I should be able to get the hang of it
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Old 25th Feb 2022, 3:56 pm   #16
SiriusHardware
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Default Re: Genuine DS1210 NVRAM controllers

The original battery was a NiMH rechargeable, if you aim to use a one-shot Lithium then it can be simplified further (no trickle charge resistor needed).
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Old 25th Feb 2022, 5:05 pm   #17
Mark1960
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Default Re: Genuine DS1210 NVRAM controllers

The maplin circuit seems to be missing a method of blocking writes to ram if the supply voltage drops, also doesn’t force a reset on supply voltage low. This would risk the processor writing over the ram on power off.
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Old 25th Feb 2022, 5:13 pm   #18
SiriusHardware
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Default Re: Genuine DS1210 NVRAM controllers

I didn't look too closely but I thought the protect-from-write on supply failure was implied by the fact that the active-low CE lines pass through the transistors, so when the power fails the RAM CE pins are disconnected from anything which can pull them low, preventing write operation.

At the same time, the battery maintains the +5V supply to the RAM but its power consumption is very low when CE is not asserted.

Having actually used that Maplin CPU (I still have it) I can't recall it ever losing or corrupting the backed up memory contents, unless of course I left it for so long that the battery ran down.
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Old 25th Feb 2022, 5:42 pm   #19
Mark1960
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Default Re: Genuine DS1210 NVRAM controllers

I think on power off the supply voltage would drop quite slowly, at least in microprocessor terms. As it drops the processor might start doing random things including writes to memory.

I might still have the schematic of a z80 processor board with 56k battery backed ram, if I can find it still. It monitored the 50Hz from the power supply to force reset and write protect if power was cut.
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Old 25th Feb 2022, 5:49 pm   #20
SiriusHardware
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Default Re: Genuine DS1210 NVRAM controllers

Unfortunately, 50Hz-AC is not one of the signals available on the MK14 rear edge connector, not even on the issue VI.
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