Dallas DS1742W Replacement

[glitchwrks]

We've been working on and off on a DS1742 replacement, apparently a bunch of Tezros showed up without them as part of some decommissioning process. Somewhere along the way, the fact that the Tezro is a 3.3V system was missed or something, because we certainly didn't realize it! System Source computer museum in Maryland loaned us a Tezro to get the prototypes ironed out though, and now we have a working module!



Despite being a 3.3V part, our replacement is 5V tolerant and can be used with cheap USB programmers like the TL866. It looks like the Tezro will properly kickstart the clock, so you don't have to worry about programming that. Using a TL866 to write data out as a DS1220 works fine. It looks like the original DS1742W 3.3V modules are also 5V tolerant, the datasheet says 6V max on VCC and does not specify if it's for the 5V or 3.3V part. We've successfully read them using a TL866 and a custom in-house device.

Incidentally, this is probably why very few people have had any success with mystery meat DS1742W chips off eBay. Our experience with buying mystery meat Dallas modules is that they're almost always remarked/relabeled counterfeits, and the 5V part appears to be much more common.

 

[Elf]

Thanks for making these, and interesting timing! It seems like we have two options on the market now

 

[weblacky]

Let us know when you'll be posting these on tindie. I have a batch DS1742W chips but I'd gladdy swap over to these for ease.

 

[CiaoTime]

Hell yeah! Count me in for at least two of them: the real things are borderline impossible to source these days.

 

[weblacky]

So I guess no one's followed up on this but it looks like these are now posted: https://www.tindie.com/products/glitchwrks/glitch-works-gw-1742w-1-dallas-ds1742w-replacement/#product-description

However it's mentioned in the description that it doesn't have the low battery indicator function and possibly have to set bit 7 of address 0x7FC to 1, yourself. I'd really like to know if in testing with the Tezro it was found that this bit set itself or is there a way under IRIX to manually write a 1 to the correct region? I don't feel like it's great that you would have to buy a compatible program or just a toggle that battery is "good" bit.

Could the original poster please update us on this new item and what tests have been done for the SGI's that take it?

 

[CiaoTime]

So I guess no one's followed up on this but it looks like these are now posted: https://www.tindie.com/products/glitchwrks/glitch-works-gw-1742w-1-dallas-ds1742w-replacement/#product-description

However it's mentioned in the description that it doesn't have the low battery indicator function and possibly have to set bit 7 of address 0x7FC to 1, yourself. I'd really like to know if in testing with the Tezro it was found that this bit set itself or is there a way under IRIX to manually write a 1 to the correct region? I don't feel like it's great that you would have to buy a compatible program or just a toggle that battery is "good" bit.

Could the original poster please update us on this new item and what tests have been done for the SGI's that take it?

Ordered a pair of them myself for Origin 350 testing! I'll let you know how that goes once they arrive.

I do have to inquire what it is that requires a low battery indicator function, though, considering that no SGI system ever came with one to my knowledge.

 

[weblacky]

I don’t know that 100% and if there is a check I don’t want a low battery warning all the time just because the region is 0 and influencing something. Since the SGI’s were designed for very specific RTC‘s I have no idea how anyone knows that they don’t use that function, since that function was included in the originals.

For all I know it does that check deep inside some routine. Unless someone can prove to me that they’ve dissected the assembly of the L1 and can show that it’s never touched I would assume it’s used somewhere in there as a troubleshooting or indicator flag in some scenario.

Just because no one has reported seeing a line of text that warns of a low battery on the L1 doesn’t mean the function isn’t used.

Since were talking about an emulation here, I’d like it to be complete as possible. If all I have to do is set the memory region to one and future tests work that’s fine, I just want to ask how much testing has been done so that this is known. The site only says Tezro seems to work, so what about Fuel or the like?

 

[Nezo1283]

Hello,

I recently purchased this module (GW-1742-1) to replace the IC DS1742W-120 which was originally in a TDS3032 oscilloscope. I wanted to change this module because the date and time of my oscilloscope no longer remained up to date. After replacing the DS1742W-120, the date and time are recorded, but now I can no longer communicate via Ethernet on the oscilloscope. I use Ethernet communication to be able to retrieve screens

I tried to program the GW-1742-1 module by copying the data from the DS1742W-120 and pasting it with an "ALL-100" programmer. Unfortunately, I cannot do this manipulation. Writing to the module does not work.

Do you know how can I repair this problem ?

Thank you in advance !